Introduction-to-Embedded-System-S.Y.B.Sc.I.T-Semester-4-munotes

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1Chapter 1: Embedded System: An Introduction
1Unit 1
1 EMBEDDED SYSTEM: AN INTRODUCTION Unit Structure
1.0 Objectives
1.1 Introduction
1.2 Definition of Embedded System
1.3 History of Embedded System
1.4 Embedded System & General -purpose computer
1.5 Classification of Embedded System
1.6 Application of Embedded System
1.7 Purpose of Embedded System
1.8 Review Questions
1.9 References & Further Reading
1.0 Objective s
• To understand what is an Embedded System and then define it
• Look at embedded systems from a historical point of view
• Classify embedded systems
• Look at certain applications & purposes of embedded systems
1.1 Introduction
This chapter introduces the reader to the world of embedded systems. Everything
that we look around us today is electronic. The days are gone where almost
everything was manual. Now even the food that we eat is cooked with the assistance
of a microchip (oven) and the ease at which we wash our clothes is due to the
washing machine. This world of electronic items is made up of embedded system.
In this c hapter we will understand the basics of embedded system right from its
definition.
1.2 Definition of An Embedded System
• An embedded system is a combination of 3 things:
a. Hardware
b. Software
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2INTRODUCTION TO EMBEDDED SYSTEMS
And it is supposed to do one specific task only.
Example 1: Washing Machine
A washing machine from an embedded systems point of view has:
a. Hardware: Buttons, Display & buzzer, electronic circuitry.
b. Software: It has a chip on the circuit that holds the software which
drives controls & monitors the various operations possible.
c. Mechanical Components: the internals of a washing machine which
actually wash the clothes control the input and output of water, the
chassis itself.
• Example 2: Air Conditioner
An Air Conditioner from an embedded systems point of view has:
a. Hardware: Remote, Display & buzzer, Infrared Sensors, electronic
circuitry.
b. Software: It has a chip on the circuit that holds the software which
drives controls & monitors the various operations possible. The software monitors the external temperature through the sensors and
then releases the coolant or suppresses it.
c. Mechanical Components: the internals of an air conditioner the motor,
the chassis, the outlet, etc
• An embedded system is design ed to do a specific job only. Example: a washing
machine can only wash clothes, an air conditioner can control the temperature
in the room in which it is placed.
• The hardware & mechanical components will consist all the physically visible
things that are u sed for input, output, etc.
• An embedded system will always have a chip (either microprocessor or
microcontroller) that has the code or software which drives the system.
1.3 History of Embedded System
• The first recognized embedded system is the Apollo Guidance
Computer(AGC) developed by MIT lab.
• AGC was designed on 4K words of ROM & 256 words of RAM.
• The clock frequency of first microchip used in AGC was
• 1.024 MHz.
• The computing unit of AGC consists of 11 instructions and 16 bit word logic. munotes.in

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3Chapter 1: Embedded System: An Introduction
• It used 5000 ICs.
• The UI of AGC is known DSKY(display/keyboard) which resembles a
calculator type keypad with array of numerals.
• The first mass -produced embedded system was guidan ce computer for the
Minuteman -I missile in 1961.
• In the year 1971 Intel introduced the world's first microprocessor chip called
the 4004, was designed for use in business calculators. It was produced by the
Japanese company Busicom.
1.4 Embedded System & General Purpose Computer
The Embedded System and the General purpose computer are at two extremes. The
embedded system is designed to perform a specific task whereas as per definition
the general purpose computer is meant for general use. It can b e used for playing
games, watching movies, creating software, work on documents or spreadsheets
etc.
Following are certain specific points of difference between
embedded systems and general purpose computers: Criteria General Computer Purpose Embedded system Contents It is combination of generic hardware and a general
purpose OS for executing a
variety of applications. It is combination of special purpose hardware and embedded OS for executing specific set of applications Operating System It contains general purpose operating system It may or may not contain operating system. Alterations Applications are alterable by the user. Applications are non-alterable by the user. Key factor Performance” factor. is key Application specific requirements are key factors. Power Consumpti on More Less Response Time Not Critical Critical applications for some munotes.in

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4INTRODUCTION TO EMBEDDED SYSTEMS
1.5 Classification of Embedded System
The classification of embedded system is based on following criteria's:
• On generation
• On complexity & performance
• On deterministic behaviour
• On triggering
1.5.1 On generation
1. First generation(1G):
• Built around 8bit microprocessor & microcontroller.
• Simple in hardware circuit & firmware developed.
• Examples: Digital telephone keypads.
2. Second generation(2G):
• Built around 16 -bit µp & 8-bit µc.
• They are more complex & powerful than 1G µp & µc.
• Examples: SCADA systems
3. Third generation(3G):
• Built around 32 -bit µp & 16 -bit µc.
• Concepts like Digital Signal Processors(DSPs), Application Specific
Integrated Circuits(ASICs) evolved.
• Examples: Robotics, Media, etc.
4. Fourth generation :
• Built around 64 -bit µp & 32 -bit µc.
• The concept of System on Chips (SoC), Multicore Processors evolved.
• Highly complex & very powerful.
• Examples: Smart Phones.
1.5.2 On complexity & performance
1. Small -scale:
• Simple in application need
• Performance not time-critical.
• Built around low performance & low cost 8 or 16 bit µp/µc. munotes.in

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5Chapter 1: Embedded System: An Introduction
• Example: an electronic toy
2. Medium -scale:
• Slightly complex in hardware & firmware requirement.
• Built around medium performance & low cost 16 or 32 bit µp/µc.
• Usually contain operating system.
• Examples: Industrial machines.
3. Large -scale:
• Highly complex hardware & firmware.
• Built around 32 or 64 bit RISC µp/µc or PLDs or Multicore Processors.
• Response is time -critical.
• Examples: Mission critical applications.
• 1.5.3 On deterministic behaviour
• This classification is applicable for “Real Time” systems.
• The task execution behaviour for an embedded system may be
deterministic or non-deterministic.
• Based on execution behaviour Real Time embedded systems are divided
into Hard and Soft.
1.5.4 On triggering
• Embedded systems which are “Reactive” in nature can be based on
triggering.
• Reactive systems can be:
• Event triggered
• Time triggered
1.6 Application of Embedded System
The application areas and the products in the embedded domain are countless.
1. Consumer Electronics: Camcorders, Cameras.
2. Household appliances: Washing machine, Refrigerator.
3. Automotive industry: Anti -lock breaking system(ABS), engine control.
4. Home automation & security systems: Air conditioners, sprinklers, fire
alarms.
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6INTRODUCTION TO EMBEDDED SYSTEMS
6. Computer peripherals: Printers, scanners.
7. Computer networking systems: Network routers and switches.
8. Healthcare: EEG, ECG machines.
9. Banking & Retail: Automatic teller machines, point of sales.
10. Card Readers: Barcode, smart card readers.
1.7 Purpose of Embedded System
1. Data Collection/Storage/Representation
• Embedded system designed for the purpose of data collection
performs acquisition of data from the external world.
• Data collection is usually done for storage, analysis, manipulation and
transmission.
• Data can be analog or digital.
• Embedded systems with analog data capturing techniques collect data
directly in the form of analog signal whereas embedded systems with
digital data collection mechanism converts the analog signal to the
digital signal using analog to digital converters.
• If the data is digital it can be directly captured by digital embedded
system.
• A digital camera is a typical example of an embedded
• System with data c ollection/storage/representation of data.
• Images are captured and the captured image may be stored within the
memory of the camera. The captured image can also be presented to
the user through a graphic LCD unit.
2. Data communication
• Embedded data communication systems are deployed in applications
from complex satellite communication to simple home networking
systems.
• The transmission of data is achieved either by a wire -line medium or
by a wire -less medium.
• Data can either be transmitted by analog means or by digital means.
• Wireless modules -Bluetooth, Wi-Fi.
• Wire -line modules -USB, TCP/IP.
• Network hubs, routers, switches are examples of dedicated data
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7Chapter 1: Embedded System: An Introduction
3. Data signal processing
• Embedded systems with signal process ing functionalities are
employed in applications demanding signal processing like speech
coding, audio video codec, transmission applications etc.
• A digital hearing aid is a typical example of an embedded system
employing data processing.
• Digital hearing a id improves the hearing capacity of hearing impaired
person
4. Monitoring
• All embedded products coming under the medical domain are with
monitoring functions.
• Electro cardiogram machine is intended to do the monitoring of the
heartbeat of a patient but it cannot impose control over the heartbeat.
• Other examples with monitoring function are digital CRO, digital
multi -meters, and logic analyzers.
5. Control
• A system with control functionality contains both sensors and
actuators.
• Sensors are connected to the input port for capturing the changes in
environmental variable and the actuators connected to the output port
are controlled according to the changes in the input variable.
• Air conditioner system used to control the room temperature to a
specified limit is a typical example for CONTROL purpose.
6. Application specific user interface
• Buttons, switches, keypad, lights, bells, display units etc are
application specific user interfaces.
• Mobile phone is an example of application specific user in terface.
• In mobile phone the user interface is provided through the keypad,
system speaker, vibration alert etc.
1.8 Review Questions
1. Define Embedded System with the help of Microwave Owen as an example
2. Differentiate between general purpose computers &
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8INTRODUCTION TO EMBEDDED SYSTEMS
3. Give a classification of embedded systems
4. List some applications of embedded systems
5. Explain the various possible purposes of using and
embedded system.
1.9 References & Further Reading
1. Programming Embedded systems in C++ by Michael Barr
2. Introduction to Embedded systems – Shibu K. V

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9Chapter 2: Core of Embedded System
9Unit 1
2 CORE OF EMBEDDED SYSTEM
Unit Structure
2.0 Objective
2.1 Difference between Microprocessor and Microcontroller
2.2 RISC (Reduced Instruction Set Computing)
2.3 CISC (Complex Instruction Set Computing)
2.3.1 Difference between RISC and CISC
2.4 Big Endian and Little Endian
2.5 Types of Processor
2.6 Commercial Off The Shelf Components (Cots )
2.7 Sensors
2.8 Actuators
2.9 Communication Interface
2.9.1 I2C BUS
2.9.2 Serial Peripheral Interface (SPI) BUS
2.9.3 Universal Asynchronous Receiver Transmitter (UART)
2.9.4 1-Wire Interface
2.9.5 Parallel – Interface
2.9.6 RS – 232
2.9.7 USB (Universal Serial Bus)
2.10 Other Types of Communication Interfaces
2.10.1 Infrared
2.10.2 Bluetooth
2.10.3 Wi-Fi (Wireless Fidelity)
2.11 Embedded -Firmware
2.12 Other System Components
2.12.1 Oscillator circuit
2.12.2 Reset Circuit
2.12.3 Watchdog timer
2.12.4 Brownout Protection circuit
2.12.5 PCB (Printed Circuit Board)
2.13 Chapter End Questions
2.14 Summary
2.15 Refer ence for further reading munotes.in

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2.0 Objective s
xFrom this chapter student will be able to explain difference between microprocessor and controller
xStudents will gain the knowledge different communication interfaces.
xStudents will be able to explain working of various communication devices
associated with embedded system
2.1 Difference between Microprocessor and Microcontroller : Micro-processor Micro-controller 1. In general, a microprocessor is a general -purpose device that finds
its application in most of the electronic devices.
2. It is a dependent unit that requires other chips for its operation.
3. Microprocessor is an I.C. which
contains many useful functions.
4. It requires external memory device to store set of instructions
to carry out user -defined task.
5. Example : - 8085. 1. Microcontroller is a specific purpose device which has specific task for specific device.
2. It is an independent device that does not require any other specific chips.
3. It is called as microchip which contains the components of microprocessor.
4. It has the ability to execute a stored set of instruction to carry
out user -defined task.
5. Example : - 8051.
2.2 RISC (Reduced Instruction Set Computing)
xRISC is designed to perform smaller number of types of computer
instructions so that it can operate at higher speed.
xThe range of instruction is 30 to 40.
xSince each instruction type that a computer must perform requires additional
transistors and circuitry a large list or a set of computer instruction tends to
make microprocessor more complicated and slower in operation.
xIt is a type of microprocessor architecture that utilizes a small highly
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11Chapter 2: Core of Embedded System
often found n other types of architecture.
xJOHN COCKE of IBM invented the RISC concept in 1974 by providing that
20% of the instruction in a computer did 80% of its work.
xMACINTOSH computer uses RISC microcomputers.
2.3 CISC (Complex Instruction Set Computing)
xA comple [LQVWUXFWLRQVHWFRPSXWHU&,6&ޖVܼVNLVDFRPSXWHULQZKLFK
single instructions can execute several low -level operations (such as a load
from memory, an arithmetic operation, and a memory store) or are capable
of multi -step operations or addressing mo des within single instructions.
xThe term was retroactively coined in contrast to reduced instruction set
computer (RISC) and has therefore become something of an umbrella term for everything that is not RISC, from large and complex mainframe computers to simplistic microcontrollers where memory load and store
operations are not separated from arithmetic instructions.
xA modern RISC processor can therefore be much more complex than, say, a
modern microcontroller using a CISC -labeled instruction set, especially in
the complexity of its el ectronic circuits, but also in the number of instructions
or the complexity of their encoding patterns.
xThe only typical differentiating characteristic is that most RISC designs use
uniform instruction length for almost all instructions, and employ stri ctly
separate load/store -instructions.
2.3.1 Difference between RISC and CISC Sr.No. RISC CISC 1 Multiple register set often consisting of more than 256 registers. Single register set, typically 6 to 16 registers total. 2 Three register operand allowed per instruction(eg. Add R1,R2,R3) Only one or two register operands allowed per instruction(eg. Add R1,R2) 3 Parameter passing through efficient on -chip register windows. Parameter passing through inefficient off -chip register windows. munotes.in

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12INTRODUCTION TO EMBEDDED SYSTEMS4 Single cycle instruction except for load and store instruction Multiple cycle instruction 5 Hardwired controlled Microprogrammed controlled 6 Highly pipelined Less pipelined 7 Fixed length of instruction (30-40 instruction) Variable length instruction 8 Only load and store instruction can access memory Many instructions can access memory. 9 Few addressing modes Many addressing modes. 2.4 Big Endian And Little Endian
xBE and LE are terms that describes the order in which the sequence of bytes
(group of 8 bi ts) are stored in computer memory.
xBE is an order in which BIG END (MSB) is stored first at the lowest storage
address while LSB is stored at the higher storage address.
xFor ex -If we want to store 5678H at memory locations 2002H and 2003H
than the orde r of storage will be 2002H=56H,2003H=78H.
xLE is an order in which LITTELE END (LSB) is stored first at the lowest
storage address while MSB is stored at the higher storage address.
xFor ex -If we want to store 5678H at memory locations 2002H and 2003H
than the order of storage will be 2002H=78H,2003H=56H.
2.5 Types of Processors
1. GENERAL PURPOSE and DOMAIN SPECIFIC PROCESSOR .
xAlmost 80% of embedded system is based on microprocessor or
microcontroller.
xMost of the embedded system is used in industry as well as those
involving monitoring applications makes use of microprocessor and
microcontroller.
xApplications requires signal processing such as speech coding ,such as
speech recognition makes use of special kind of digital signal process or
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13Chapter 2: Core of Embedded System
2. APPLICATION SPECIFIC INTEGRATED CIRCIUT (ASIC)
xASIC is a microchip designed to perform some specific function or
task.
xIt is basically a microchip customized for a particular use rather than
intended for general purpose use.
xFor ex -A ch ip design solely to run a cell phone is an ASIC.
xASIC are categorized according to the technology used for manufacturing. Hence ,are the following types of ASIC :
i. FULLY -CUSTOMIZED ASIC
¾Fully -customized ASIC are those IC’s which cannot be modified
to suit different applications.
¾Fully customized ASIC’s are those that are entirely tailor filtered
to a particular application.
¾Since its ultimate design and functionality is pre -specified by the
user.
¾The use of pre -defined mask for manufacturing leaves no option
for circuit modification during fabrication except for some minor
fine tunings or calibration and is generally produced as a s ingle
specific product for a particular application only.
ii. SEMI -CUSTOMIZED ASIC
¾These ASIC can be modified partially to serve different functions
within its general area of application.
¾Unlike fully -customized ASIC, semi -customized ASIC are designed to allow certain degree of modification during manufacturing process.
iii. STRUCTURED/PLATFORM ASIC
¾Structured or platform ASICs belongs to relatively new ASIC
classification.
¾These are those ASIC which have been designed and produced
from a t ightly defined set of designed methodologies, intellectual
properties and well characterized silicon.
¾The aim to developed this type of ASIC is to shorten design cycle
and minimizing development cost.
¾A platform ASIC is built from group of platform sli ces with a
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3. PROGRAMMABLE LOGIC DEVICE (PLD)
xIn digital electronic system there are only three kinds of devices that
are memory, microprocessor and logic device s.
xMemory devices store random information such as database.
xMicroprocessor executes software instruction to perform a wide variety
of tasks such as running a word processing program or a video game.
xLogic devices provide specific function including device to device
interfacing data communication. Signal processing data display
timing and control operations and almost every other function assistive
must perform.
xPLD is an electronic component use to build re -configurable digital
circuit .
xUn-like a logic gate which has fixed function a PLD has un -defined
function at the time of manufacture.
xBefore a PLD can use in a circuit it must be programmed i.e. re -
configured.
xPLD’s are chip that can be programmed and reprogrammed to
implemente d different logic function.
xThe main reason to produce PLD is to reduce total cost.
xDesigning with PLD is faster due to which it reduces the time require
to bring the product to the market.
xIt also reduces the risk associated with the product develop ment since
they allow last minute changes without having to re -designed circuit
boards.
xThere are two types of PLD’s:
i. Fixed logic device (FLD)
ii. Programmable logic device (PLD)
xADVANTAGES OF PLD
¾Less board space is required
¾Faster in speed.
¾Lower power requirement.
¾Less costly assembly process.
¾Higher reliability (since fewer IC’s) and circuit connections are
there which helps in making troubleshooting easier.
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xDISADVANTAGES OF PLD
¾PLD’s required additional development software and hardware which
is often very expensive.
¾Design staff often needs to be trained to use new design tools. In
addition, parts must be programmed before they can be assembling into
a final product.
2.6 Commercial Off The Shelf Components (COTS)
xCOTS describes software and hardware product that are ready made and
available for sale to the general public.
xFor ex -Microsoft office is a COTS product i.e. packaged software solution
for businesses.
xCOTS products are designed to be implemented easily into existing system
without need of customization.
xRe-using components made for earlier product as an approach to new system
development is a promising way of achieving the mention development and
system improvement.
xThere is also possibility to buy software components from component
vendors.
xThe use of COTS, software component is increasing in today’s development
of new system.
xShorter systems life cycle and decreased development budget has made
COTS necessary.
xCOTS component can also provide an increased reliability compared to
customize made components since they are redefined by substantial field
testing.
xAlthough using COTS component can save valuable development time,
insight in the COTS component functionality and properties must be evaluated for its intended use.
xIn order to integrate COTS component in a system the developer must
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2.7 Sensors
xSensors are also called as detectors.
xIt is a device that measures a physical quantity and converts It into a signal
which can be read by an observer or by an instrument.
xIn other words, we can say that sensors are electronic devices made to sense
physical quantities.
xThe sensor can be defined as a transducer that converts energy from one t ype
to another type for any particular purpose.
xExample: -
i. A mercury in a glass thermometer converts the measured temperature
into expansion and contraction of a liquid which can be read on
calibrated glass tube.
ii. A thermocouple is a heat sensor t hat converts temperature to an output
voltage which can be read by voltmeter.
xFor accuracy, most sensors are calibrated against known standards.
xThe sensors are widely used embedded systems so that the system can sense
the external physical behaviour a nd the system can take action accordingly.
xExample: - Optical light, pressure sensor, proximity sensor, gyroscope
sensor, ambient -light sensor, etc.
2.8 Actuators
xAn actuator is a device that converts energy into motion.
xIt can also be used to apply force.
xAn actuator is a mechanical device that takes energy, that is created by air,
electricity or liquid and convert it into some kind of motion. This motion can
be virtually in any form such as blocking, clamping(cutting), ejecting, or
many other typ es of motion.
xActuators are used in manufacturing or industrial application and might be
used in devices such as motors, pumps, switches and valves.
xAn actuator can be defined as mechanical device used for moving or
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xIt is operated by a source of energy usually in form of electric current,
hydraulic fluid or pneumatic pressure and converts that energy into some kind
of motion.
2.9 Communication Interface :
xCommunication Interface is necessary for communicating with various sub -
systems of the embedded systems and with external world.
xThe communication system can be classified into 2 types: -
(i) On-board communication interface
(ii) External communication interface
xExamples of on -board communic ation interface are : -
I2C - Inter Integrated Circuit
SPI – Serial Peripheral Interface
UART – Universal Asynchronous Receiver Transmitter,
One Wire Interface, etc.
xExample of external communication interface are : -
RS232 C,
USB – Universal Serial Bus,
Ethernet, etc.
2.9.1 I2C BUS

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xI2C BUS is a bi -directional 2 -wire serial BUS that provides communication
link between integrated circuits.
xIt was designed by Phillips in the early 80’s to allow communication between
components w hich are on the same circuit board.
xThe two bi -directional lines used for communication are Serial Data Line
(SDA) and Serial Clockwise (SCL) as shown in the above diagram.
xThese are 3 data -transfer speed for I2C BUS
i.e. Standard (100 kbps)
Fast mode (400 kbps)
High Speed (3.4 mbps)
xFeatures of I2C : -
1. Only 2 BUS lines are required.
2. Supports various data speed rates.
3. It provides a simple master -slave relationship.
4. There is a provision for collision detection.
5. It support s data broadcast.
2.9.2 Serial Peripheral Interface(SPI) BUS

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xSPI is a synchronous serial data link which works in full duplex mode.
xIt is a serial interface in which 4 wires are required for communication.
xIt works on the Master -slave principle whe re it can have multiple slave.
xThe four wires used for communication are as follows : -
(i) SCK – Serial Clock Line
(ii) MOSI/SDI (Master Output Slave Input / Slave Data Input)
(iii) MISO/SDO (Master Input Slave Output/ Slave Data Output)
(iv) SS / CS (Chip Select)
• Disadvantages of SPI BUS : -
1) It requires more number of pins.
2) During data transfer, there is no acknowledgement from the slave.
3) There is no provision for error checking.
4) It supports only 1 Master.
5) Noise may affect or cor rupt the data.
2.9.3 Universal Asynchronous Receiver Transmitter (UART)
xIt is a computer hardware that translates data between parallel & serial forms.
xUART is used in conjunction with communication standards such as RS -232,
RS-422, etc.
xIt converts the bytes received from computer along parallel circuits into a
single serial bit stream for outgoing transmissions.
xFor incoming transmissions, it converts the serial bit stream into the bytes
that computer handles.
xIt adds a parity bit on the outgoin g transmission & checks the parity of
incoming bytes and then discard the parity bit.
xIt adds start and stop bits on outgoing signals & separate them from incoming
signal.
xIt handles interrupt from keyboard and mouse.
xIt may handle other kinds of int errupt & device management that requires
coordinating the computer speed of operation with device speed.
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2.9.4 1 -Wire Interface

x1 – wire interface is an asynchronous half duplex communication protocol.
xIt makes use of a single wire or a line called as “DQ” for communications
and follows master -slave model.
xThis type of interface supports a single master and 1 or more slaves.
xThe network design for 1 -wire interface can be linear -topology, star topology
and stubbed topology.
xThe sequence o f operation for communicating with a 1 -wire slave is as
follows:
(i) The master device sends a reset pulse on 1 -wire bus.
(ii) The slave device responds with a present pulse.
(iii) The master device sends a command and 64 -bit address of the slave
device to which master wants to communicate.
(iv) The master device sends a read/write function command to read/write
the internal memory or register of the slave device.
(v) After sending read/write function, the master initiates the given operation.


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2.9.5 Parallel – Interface:

xIn this type of interface, the host microcontroller/microprocessor contains a
parallel BUS & the devices which supports such an interface.
xThe communication through the parallel BUS is controlled by the control
signals such as Read, Write, and Chip Select.
xWhen the address selected by the processor is within the range, the decoder
circuit activates the Chip Select line & the device becomes active.
xWhile applying proper control signal, the processor can either write into the
device or read from the device.
xThe width of the BUS can be 4 -bit, 8 -bit, 16 -bit, 32 -bit or 64 -bit.
2.9.6 RS – 232
xRS-232 was introduced in the year 1962, where the signals were represented
by voltage -level with respect to a system.
xIt is a single -ended (1 -wire) independent channel used for full duplex
communication.
xThis interface was developed by EIA(Electronic Industry Association).
xAs per EIA standards, any voltage between +3V to +12V is logic 0, while
any voltage between -3V to -12V is logic 1.
xRS-232 C standard defines many hand -shaking and control signal.
xIt supports 2 different types of connectors, i.e. DB 9 & DB 25.
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xRS-232 C is a point to point communication interface and devices involved
for communication are called as Data Terminal Equipment (DTE) & Data
Communication Equipment (DCE).
xThis interface gives a speed of about 300 bps (bits per second) to about 20
kbps (kilobits per second).
xThe maximum operating distance supported by RS -232 C is about 50 feet.
xDisadvantages :
1) Suitable for system -to-system communication & NOT for chip to chip
or chip to sensor.
2) Low speed for long distance.
3) Requires transceiver (transmitter + receiver) chips which add to system
cost.
4) Supports only single master -single slave interface.
2.9.7 USB (Universal Serial Bus) :
xUSB is wired high speed serial bus for data communication.
xUSB was originally developed in the year 1995 by its core -group members
consisting of Microsoft, Intel, IBM, Compaq and Northern Telecom.
xUSB communication system follows a Star -topology with the USB Host at
the centre and one or more USB peripheral devices connected to it.
xA USB host can support a connection of upto 127 slave devices.
xUSB transmits data in packet format where each packe t data has a standard
format.
xThe physical connection between a USB device and a master device is done
by using a USB port / USB cable.
xThe USB cable supports communication upto a distance of 5 meters.
xThere are 2 types of connectors : Type -A and Typ e-B for USB connections.
xThe USB connection present in PCs & laptops are example of type -A
connectors, and type -B connectors contains 4 pins for communication.
xDifferential signals are used for data transmissions; hence we get good noise
immunity.
xUSB interface has the ability to supply power to the connecting devices.
xUSB devices supports different data rates such as low speed (1.5 mbps), full
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2.10 Other Types of Communication Inte rfaces
2.10.1 Infrared
xInfrared is a serial half -duplex line -of-sight base wireless technology used for
data communication between devices.
xFor infrared communication, a transceiver must be present in both the
devices.
xIn this technique, infrared wav es of the electromagnetic spectrum are used
for transmitting the data.
xIt supports point to point and point to multi -point communication, provided
all the devices in the communication are within line -of-sight.
xThe typical range for communication is fro m 10cm to 3m, depending upon
transmitting power.
xIR supports data rates from 9.6 kbps to 16 mbps.
xDepending upon the speed of transmission, IR is classified into serial IR,
medium IR, fast IR, very fast IR, and ultra -fast IR.
xIR communication has an L.E.D. at the transmitter -end and a photodiode at
the receiver -end.
2.10.2 Bluetooth
xBluetooth is a wireless protocol utilizing short -range communication technology felicitating data transmission over short distance from fixed and
/ or mobile devices creating wireless Personal Area Network (PAN).
xThe objective behind development of Bluetooth was the creation of a single -digit wireless protocol capable of connecting multiple devices and overcoming issues arising from synchronization of these devices.
xBluetooth operates on 2.4 GHz of radio -frequency spectrum, and uses
technique called as Frequency Hopping Spread Spectrum (FHSS).
xIt provides a data rate of upto 1 mbps and range of approximately 30 feet.
xBluetooth supports point t o point wireless communication.
xThe point -to-point communication follows the master -slave relationship.
xWhen a network is formed in such a way that it contains one master and more
than one slave, then it is called as piconet.
xA piconet supports maximum of 7 slave devices.
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xAdvantages :
1) Bluetooth devices are wireless.
2) It is inexpensive.
3) Bluetooth is automatic.
4) Inter -operability.
5) Low interference.
6) Low energy consumption.
7) Shares voice and data.
8) Makes use of instant PAN (Personal Area Network).
9) Upgradable.
2.10.3 Wi -Fi (Wireless Fidelity)
xWi-fi is a popular wireless communication technique for devices involved in
network communication.
xWi-fi supports Internet Protocol (IP) , based communication.
xIn an IP-based communication, each device is identified by an IP -address
which is unique for each device of the network.
xWi-fi based communication requires Wi -fi router to manage communication.
xThis router is responsible for providing access to the network, assigning IP
address to the device of the network & routing data packets to the devices.
xWi-fi operates at a frequency of 2.4 GHz or 5 GHz of the radio -spectrum.
xWi-fi supports data rates ranging from 1 mbps to 150 mbps and it offers the
range of abou t 300 feet.
2.11 Embedded -Firmware
xEmbedded firmware refers to control algorithm or the program instruction
written by the programmer & dumped (stored) into the code memory of the
embedded system.
xThere are various methods for developing embedded firmw are which are as
follows:
(i) Writing the program in high -level languages like C, C++ & using
Integrated Development Environment (IDE).
(ii) The IDE contains editor, compiler, debugger, etc.
(iii) Writing the program in assembly language.
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xThe process of converting the program written in either high -level language
or assembly language to machine language is called hex -file creation.
xFor writing embedded firmware, higher -level language is preferred over
assembly language because of following re asons : -
(i) Writing codes in high -level language is easy.
(ii) The code written in high -level language is easily portable.
(iii) It is easy to debug a high -level language program.
(iv) Developing assembly level language program is very tedious & time
consuming.
2.12 Other System Components
xWhile designing an embedded system, we also need supporting circuits or
components for proper functioning of embedded system.
xFollowing are some of the important components:
1) Oscillator circuit
2) Reset circuit
3) Watchdog circuit
4) Brownout protection
5) PCB (Printed Circuit Board)
2.12.1 Oscillator circuit

xOscillator circuit is used for providing clock frequency to microprocessor or
microcontroller so that they can execute program or program instructions.
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xTo generate a clock frequency, a quartz crystal oscillator is connected to
microprocessor or microcontroller.
xThe instruction execution of a microprocessor/microcontroller occurs in
synchronization with a clock signal.
xIn embedded syste m, the oscillator circuit is responsible for generating the
exact clock for microprocessor/microcontroller.
xThere are certain processors or controllers that have built -in oscillator and
simply requires an external resonator or quartz crystal for producin g
necessary clock signal.

2.12.2 Reset Circuit
xReset means that the processor starts the processing of the instruction from a
starting address.
xThe address is one that is set by default in the processor program counter.
xThe reset circuit is essentia l to ensure that the device is not operating at the
voltage level where device is not guaranteed to operate when the system is
just started.
xThe reset signal brings the external register and the different hardware system
of the microprocessor/microcontro ller to a known state and starts the
firmware execution from the reset address.
2.12.3 Watchdog timer
xMost of the embedded systems need to be self -relying. It is not usually
possible to wait for someone to reboot them if the system hangs.
xSome embedded designs such as space probes are simply not accessible to
human operator.
xIf their software ever hangs, such systems are permanently disabled.
xIn other cases, the speed with which a human operator might reset the system
would be too slow to me et the uptime requirements of the product.
xA watchdog timer is a piece of hardware that can be used to automatically
detect software abnormalities and reset the processor if required.
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27Chapter 2: Core of Embedded System

xIn the diagram it is seen that watchdog timer is a chip external to the processor
however it could also be included within the same chip as the CPU.
This is done in many microcontrollers.
In either cases , the output from watchdog timer is tied/connected directly to
the processor’s reset signal.
xKicking the dog is nothing but the process of restarting the watchdog timer
counter by software.
xThe software must restart the watchdog timer at regular rate o therwise, there
is a risk if the system being restarted.
xA watchdog timer is a useful tool in helping the system to recover from
failures.
2.12.4 Brownout Protection circuit
xBrownout protection circuit is used to protect microprocessor/microcontroller from unexpected program execution when
the input voltage to processor or controller falls down to a specified voltage.
xMostly all microcontrollers have built in brown -out detection (BOD) circuit
which monitors supply voltage level during operation.
xBOD circuit is a comparator which compares supply voltage t a fixed trigger
level.
xThere are 2 types of Brownout protection circuits : -
(a) On-chip
(b) External / off -chip

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2.12.5 PCB (Printed Circuit Board)
xPCB is used to mechanically support and electrically connect electronic
components using conduction parts, tracks or signal traces etched from
copper sheets laminated on a non -conductive surface.
xPCB is the backbone of every embedded system.
xAfter finalizing the components and inter -connecti ons between them, a schematic diagram is created and according to the diagram, PCB is fabricated.
xPCB acts as a platform for placing all the necessary components as per the
design requirement.
2.13 Chapter End Questions
Answer the following questions.
1. Differentiate between RISC and CISC
2. Differentiate between Microprocessor and Microcontroller
3. Explain Big Endian and Little Endian
4. Explain ASIC in details.
5. Explain PLD
6. Explain sensors and actuators.
7. Explain I2C BUS and SPI BUS
8. Explai n the function of watchdog timer in details.
9. Explain Bluetooth and WIFI
10. Explain RS 232 C
2.14 Summary
xFrom the chapter we have explained in detail working of various communication interface devices.
xDifferentiated microprocessor and microcontroller
xUnderstood various types of processors
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29Chapter 2: Core of Embedded System
2.15 Reference for further reading
• Introduction to embedded systems by Shibu K V
xEmbedded Systems by Rajkamal
xBluetooth - Wikipedia
xFirmware vs Embedded Software - What's the difference? (andplus.com)

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30INTRODUCTION TO EMBEDDED SYSTEMS
30Unit 1
3 CHARACTERISTICS & QUALITY
ATTRIBUTES OF EMBEDDED SYSTEMS
Unit Structure
3.0 Objectives
3.1 Introduction
3.2 Characteristics of Embedded System
3.3 Quality Attributes of Embedded System
3.3.1 Operational Attributes
3.3.2 Non-Operational Attributes
3.4 Review Questions
3.5 References & Further Reading
3.0 Objective s
After reading this chapter you will:
1. Understand the characteristics of Embedded system
2. Understand the attributes related to quality of embedded system.
3.1 Introduction
The characteristics of embedded system are different from those of a general -
purpose computer and so are its Quality metrics. This chapter gives a brief
introduction on the characteristics of an embedded system and the attributes that
are associated with its quality.
3.2 Characteristics of Embedded System s
Following are some of the charac teristics of an embedded system that make it
different from a general -purpose computer:
1. Application and Domain specific
z An embedded system is designed for a specific purpose only. It will not
do any other task.
z Ex. A washing machine can only wash, it cannot cook
z Certain embedded systems are specific to a domain: ex. A hearing aid
is an application that belongs to the domain of signal processing.
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2. Reactive and Real time
z Certain Embedded systems are designed to react to the events that
occur in the nearby environment. These events also occur real -time.
z Ex. An air conditioner adjusts its mechanical parts as soon as it gets a
signal from its sensors to increase or decrease the temperature when the
user operates it using a remote con trol.
z An embedded system uses Sensors to take inputs and has actuators to
bring out the required functionality.
3. Operation in harsh environment
z Certain embedded systems are designed to operate in harsh environments like very high temperature of the d eserts or very low
temperature of the mountains or extreme rains.
z These embedded systems have to be capable of sustaining the environmental conditions it is designed to operate in.
4. Distributed
z Certain embedded systems are part of a larger system and thus form
components of a distributed system.
z These components are independent of each other but have to work
together for the larger system to function properly.
z Ex. A car has many embedded systems controlled to its dash board.
Each one is an independent embedded system yet the entire car can be
said to function properly only if all the systems work together.
5. Small size and weight
z An embedded system that is compact in size and has light weight will
be desirable or more popular than one tha t is bulky and heavy.
z Ex. Currently available cell phones. The cell phones that have the
maximum features are popular but also their size and weight is an
important characteristic.
z For convenience users prefer mobile phones than phablets. (phone +
tablet pc)
6. Power concerns
z It is desirable that the power utilization and heat dissipation of any
embedded system be low.
z If more heat is dissipated then additional units like heat sinks or cooling
fans need to be added to the circuit.
z If more power is required then a battery of higher power or more
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3.3 Quality Attributes of Embedded System s
These are the attributes that together form the deciding factor about the quality of
an embedded system.
There are two types of quality attributes are: -
1. Operational Quality Attributes.
z These are attributes related to operation or functioning of an embedded
system. The way an embedded system operates affects its overall
quality.
2. Non-Operational Quality Attributes.
z These are attributes not related to operation or functioning of an
embedded system. The way an embedded system operates affects its
overall quality.
z These are the attributes that are associated with the embedded syst em
before it can be put in operation.
3.3.1 Operational Attributes
a) Response
z Response is a measure of quickness of the system.
z It gives you an idea about how fast your system is tracking the input
variables.
z Most of the embedded system demand fast response which should be
real-time.
b) Throughput
z Throughput deals with the efficiency of system.
z It can be defined as rate of production or process of a defined process
over a stated period of time.
z In case of card reader like the ones used in buses, throughput means
how much transaction the reader can perform in a minute or hour or
day.
c) Reliability
z Reliability is a measure of how much percentage you rely upon the
proper functioning of the system.
z Mean Time between failures and Mean Time To Repair are terms used
in defining system reliability.
z Mean Time between failures can be defined as the average time the
system is functioning before a failure occurs.
z Mean time to repair can be defined as the average time the system has
spent in repairs.
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d) Maintainability
z Maintainability deals with support and maintenance to the end user or
a client in case of technical issues and product failures or on the basis
of a routine system checkup
z It can be classified into two types : -
1. Scheduled or Periodic Maintenance
o This is the maintenance that is required
regularly after a periodic time interval.
o Example :
z Periodic Cleaning of Air Conditioners
z Refilling of printer cartridges.
2. Maintenance to unexpected failure
z This involves the maintenance due to a sudden breakdown in
the functioning of the system.
z Example:
1. Air conditioner not powering on
2. Printer not taking paper in spite of a full paper stack
e) Security
z Confidentiality, Integrity and Availability are three corner stones of
information security.
z Confidentiality deals with protection data from unauthorized disclosure.
z Integrity gives protection from unauthorized modification.
z Availability gives protection from unauthorized user
z Certain Embedded systems have to make sure they conform to the
security measures. Ex. An Electronic Safety Deposit Locker can be
used only with a pin number like a password.
f) Safety
z Safety deals with the possible damage that can happen to the operating
person and environment due to the breakdown of an embedded system
or due to the emission of hazardous materials from the embedded
products.
z A safety analysis is a must in product engineering to evaluate the
anticipated damage and determine the best course of action to bring
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3.3.2 Non Operational Attributes
a) Testability and Debug -ability
z It deals with how easily one can test his/her design, application and by
which mean he/she can test it.
z In hardware testing the peripherals and total hardware function in
designed manner
z Firmware testing is functioning in expected way
z Debug -ability is means of debugging the product as such for figuring
out the probable sources that create unex pected behavior in the total
system
b) Evolvability
z For embedded system, the qualitative attribute “Evolvability” refer to
ease with which the embedded product can be modified to take
advantage of new firmware or hardware technology.
c) Portability
z Portability is measured of “system Independence”.
z An embedded product can be called portable if it is capable of performing its operation as it is intended to do in various environments
irrespective of different processor and or controller and embedded
operating systems.
d) Time to prototype and market
z Time to Market is the time elapsed between the conceptualization of a
product and time at which the product is ready for selling or use
z Product prototyping help in reducing time to market.
z Prototyping is an informal kind of rapid product development in which
important feature of the under consider are develop.
z In order to shorten the time to prototype, make use of all possible option
like use of reuse, off the s helf component etc.
e) Per unit and total cost
z Cost is an important factor which needs to be carefully monitored.
Proper market study and cost benefit analysis should be carried out
before taking decision on the per unit cost of the embedded product.
z When the product is introduced in the market, for the initial period the
sales and revenue will be low
z There won’t be much competition when the product sales and revenue
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35Chapter 3: Characteristics & Quality Attributes of Embedded Systems
z During the maturing phase, the growth will be steady and revenue
reaches highest point and at retirement time there will be a drop in sales
volume.
3.4 Review Questions
3.4.1 Explain the characteristics of an embedded system
3.4.2 Explain the Operational Quality Attributes of an embedded
system
3.4.3 Explain the non-quality attributes of an embedded system
3.5 References & Further Reading
3.5.1 Programming Embedded systems in C++ by Michael Barr
3.5.2 Introduction to Embedded systems – Shibu K. V

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36INTRODUCTION TO EMBEDDED SYSTEMS
36Unit 2
4 EMBEDDED SYSTEMS -
APPLICATION AND DOMAIN SPECIFIC
Unit Structure
4.0 Objectives
4.1 Introduction
4.2 Elements of Embedded Systems.
4.3 Case studies (examples)
4.3.1 Washing machine
4.3.2 Microwave o ven
4.3.3 Automotive Embedded System (AES)
4.4 Review questions
4.5 References & further reading
4.0 Objective s
After learning this chapter, you will be able to:
1. Define and describe the elements of an embedded system
2. Understand how embedded system works with the help of two case studies:
i. Washing Machine
ii. Microwave Owen
4.1 Introduction
The previous chapter was an introduction to the world of embedded systems and
helped us define what is an embedded system.
This chapter introduces us to the elements of an embedd ed system and explains
how embedded system works with the help of two case studies.
4.2 Elements of Embedded Systems. xAs defined earlier, an embedded system is a combination of 3 things:
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37Chapter 4: Embedded Systems-Application and Domain Specific
c. Mechanical Components
And it is supposed to do one specific task only.
Diagrammatically an embedded system can be represented as follows:


Figure 2.0 : Elements of an Embedded System
xEmbedded systems are basically designed to regulate a physical variable
(such Microwave Oven) or to m anipulate the state of some devices by
sending some signals to the actuators or devices connected to the output port
system (such as temperature in Air Conditioner), in response to the input
signal provided by the end users or sensors which are connected t o the input
ports.
xHence the embedded systems can be viewed as a reactive system.
xExamples of common user interface input devices are keyboards, push
button, switches, etc.
xThe memory of the system is responsible for holding the code (control
algorithm and other important configuration details).
xAn embedded system without code (i.e. the control algorithm) implemented
memory has all the peripherals but is not capable of making decisions
depending on the situational as well as real world change s.
xMemory for implementing the code may be present on the processor or may
be implemented as a separate chip interfacing the processor In a controller
based embedded system, the controller may contain internal memory for
storing code
xSuch controllers are called Micro -controllers with on -chip ROM, eg. Atmel
AT89C51.
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4.3 Case Studies (Examples )
Here are some case studies on some commonly used embedded systems that will
help to better understand the concept.
4.3.1 Was hing Machine
Let us see the important parts of the washing machine; this will also help us
understand the working of the washing machine:
1) Water inlet control valve : Near the water inlet point of the washing there is
water inlet control valve. When you load the clothes in washing machine, this
valve gets opened automatically and it closes automatically depending on the
total quantity of the water required. The water control valve is actually the
solenoid valve.
2) Water pump : The water pump circula tes water through the washing
machine. It works in two directions, re -circulating the water during wash
cycle and draining the water during the spin cycle.
3) Tub: There are two types of tubs in the washing washing machine: inner and
outer. The clothes ar e loaded in the inner tub, where the clothes are washed,
rinsed and dried. The inner tub has small holes for draining the water. The
external tub covers the inner tub and supports it during various cycles of
clothes washing.
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4) Agitator or rotating disc : The agitator is located inside the tub of the
washing machine. It is the important part of the washing machine that
actually performs the cleaning operation of the clothes. During the wash
cycle the agitator rotates continuously and produces strong rotating currents
within the water due to which the clothes also rotate inside the tub. The
rotation of the clothes within water containing the detergent enables the
removal of the dirt particles from the fabric of the clothes. Thus the agitator
produces most impo rtant function of rubbing the clothes with each other as
well as with water.
In some washing machines, instead of the long agitator, there is a disc that
contains blades on its upper side. The rotation of the disc and the blades
produce strong currents within the water and the rubbing of clothes that helps
in removing the dirt from clothes.
5) Motor of the washing machine : The motor is coupled to the agitator or the
disc and produces it rotator motion. These are multispeed motors, whose
speed can be changed as per the requirement. In the fully automatic washing
machine the speed of the motor i.e. the agitator changes automatically as per
the load on the washing machine.
6) Timer : The timer helps setting the wash time for the clothes manua lly. In the
automatic mode the time is set automatically depending upon the number of
clothes inside the washing machine.
7) Printed circuit board (PCB) : The PCB comprises of the various electronic
components and circuits, which are programmed to perform i n unique ways
depending on the load conditions (the condition and the amount of clothes
loaded in the washing machine). They are sort of artificial intelligence
devices that sense the various external conditions and take the decisions
accordingly. These ar e also called as fuzzy logic systems. Thus, the PCB will
calculate the total weight of the clothes, and find out the quantity of water
and detergent required, and the total time required for washing the clothes.
Then they will decide the time required for washing and rinsing. The entire
processing is done on a kind of processor which may be a microprocessor or
microcontroller.
8) Drain pipe : The drain pipe enables removing the dirty water from the
washing that has been used for the washing purpose.
4.3.2 Microwave Owen
Let us see the important parts of the microwave oven; this will also help us
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Figure 2.3 : Parts of a Microwave Owen
A microwave oven consists of:
4.3.2.1 A high voltage transformer, which passes energy to the magnetron
4.3.2.2 A cavity magnetron,
4.3.2.3 A Control circuit with a microcontroller,
4.3.2.4 A waveguide, and
4.3.2.5 A cooking chamber
1. A Transformer transfers electrical energy through a circuit by magnetic
coupling without usin g motion between parts. These are used for supplying
power to the magnetron.
2. A Cavity magnetron is a microwave antenna placed in a vacuum tube and
oscillated in an electromagnetic field in order to produce high GHz
microwaves. Magnetrons are used in microwave ovens and radar systems.
3. A control circuit with a microcontroller is integrated on a circuit board. The
microcontroller controls the waveguide and the entire unit so the microwaves
are emitted at a constant rate.
4. A Waveguide is any linear s tructure that guides electromagnetic waves for
the purpose of transmitting power or signals. Generally constructed of a hollow
metal pipe. Placing a waveguide into a vacuum causes radio waves to scatter.
5. A Cooking Chamber is a microwave safe container the prevents microwaves from escaping. The door has a microwave proof mesh with holes
that are just small enough that microwaves can't pass through but lightwaves
can. The cooking chamber itself is a Faraday cage enclosure whi ch prevents
the microwaves from escaping into the environment. The oven door is usually
a glass panel for easy viewing, but has a layer of conductive mesh to maintain
the shielding.
4.3.3 Automotive Embedded System (AES)
xThe Automotive industry is one of the major application domains of
embedded systems.
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xAutomotive embedded systems are the one where electronics take control
over the mechanical system. Ex. Simple viper control.
xThe number of embedded controllers in a normal vehicle varies somewhere
between 20 to 40 and can easily be between 75 to 100 for more sophisticated
vehicles.
xOne of the first and very popular use of embedded system in automotive
industry was microprocessor -based fuel injection.
xSome of the other uses of embedded controllers in a vehicle are listed below:
a. Air Conditioner
b. Engine Control
c. Fan Control
d. Headlamp Control
e. Automatic brake system control
f. Wiper control
g. Air bag control
h. Power Windows
xAES are normally built around microcontrollers or DSPs or a hybrid of the
two and are generally known as Electronic Control Units (ECUs).
xTypes Of Electronic Control Units(ECU)
9High -speed Electronic Control Units (HECUs) :
xHECUs are deployed in critical control units requiring fast response.
xThey Include fuel injection systems, antilock brake systems, engine control,
electronic throttle, steering controls, transmission control and central control
units.
9Low Speed Electronic Control Units (LECUs): -
xThey are deployed in applications where response time is not so critical.
xThey are built around low cost microprocessors and microcontrollers and
digital signal processors.
xAudio controller, passenger and driver door locks, door glass cont rol etc.
xAutomotive Communication Buses
Embedded system used inside an automobile communicate with each other
using serial buses. This reduces the wiring required.
Following are the different types of serial Interfaces used in automotive
embedded applications:
a. Controller Area Network (CAN): -
x CAN bus was originally proposed by Robert Bosch.
x It supports medium speed and high speed data transfer
x CAN is an event driven protocol interface with support for error handling
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b. Local Interconnect Network (LIN): -
xLIN bus is single master multiple slave communication interface with
support for data rates up to 20 Kbps and is used for sensor/actuator
interfacing
xLIN bus follows the master communication triggering to eliminate the
bus arbitration problem
xLIN bus applications are mirror controls , fan controls , seat positioning
controls
c. Med ia-Oriented System Transport ( MOST): -
xMOST is targeted for automotive audio/video equipment interfacing
xA MOST bus is a multimedia fiber optics point –to- point network
implemented in a star, ring or daisy chained topology over optical fiber
cables.
xMOST bus specifications define the physical as well as application
layer , network layer and media access con trol.
4.4 Review Questions
1. What is an embedded system? What are the working elements of an
embedded system?
2. Explain the working of embedded system with respect to:
A. Washing Machine
B. MICROWAVE Owen
3. Conduct case studies for working of embedded systems for the following
topics:
A. Air Conditioner
B. Automobile
4.5 References & Further Reading
Books:
1. Programming Embedded systems in C++ by Michael Barr
2. Introduction to Embedded systems – Shibu K. V

Websites:
1. Washing Machine: http://www.brighthubengineering.com
2. Microwave O ven: http://globalmicrowave.org/microwaves.php

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43Chapter 5: Embedded Hardware
43Unit 2
5 EMBEDDED HARDWARE
Unit Structure
5.0 Objectives
5.1 Introduction
5.2 Components on an embedded system
5.3 Memory Map
5.4 I/O Map
5.5 Interrupt Map
5.6 Review Questions
5.7 References & Further Reading
5.0 Objectives
After reading this chapter you will be able to:
xUnderstand in general the difference in programming software for general
purpose computers and embedded systems
xThe way in which processor communicates with components of embedded
system
xMemory Map, I/O Map & Interrupt Map
5.1 Introduction
The software programmer must know the hardware involved in an embedded
system before he can even attempt to write code for its functioning.
Programming for embedded systems is different than programming on computers.
Embedde d systems have certain strict assumptions to be followed. Until the
programmer does not know what hardware components are involved and what are
the assumptions and rules related to those components, the program or code cannot
be written.
This chapter intro duces the reader with the hardware of embedded system from a
software perspective. It is this where the reader shall understand where the code
fits in an embedded system.
5.2 Components on an Embedded System
xBefore the programmer can start to code anything, he has to invest some time
in understand the functioning of the embedded system.
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xHe is expected to understand the following things:
5.2.1 Functioning or purpose of the embedded system
5.2.2 Individual components involved
5.2.3 The way data flo ws through the components of an embedded system.
xConsider an example of an embedded system intended to be used as a printer -
sharing device. This device is attached to a printer and allows access to two
computers through serial interface and one printer t hrough a parallel
interface.
xThe diagram below describes the way the devices are connected to each other.
Data to be printed is accepted from either serial port, held in RAM until the
printer is ready for more data, and delivered to the printer via the p arallel
port. The software that makes all of this happen is stored in ROM.
xThe working or execution of the code is brought about by the processor. The
processor knows two types of components: memory and peripherals.
xMemories are for data and code stora ge and retrieval. Ex. RAM & ROM
xPeripherals are specialized hardware devices that either coordinate interaction with the outside world (I/O) or perform a specific hardware
function. Ex. Serial Port

Figure: Components involved in an printer sharing devi ce
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45Chapter 5: Embedded Hardware
xCertain processors like intel communicate with these memories and peripherals with two distinct address spaces.
xThe first address space is called the memory space and is intended mainly for
memory devices; the second is reserved exclusively for peripherals and is
called the I/O space.
xWhen peripherals are located in I/O space they are called I/O Mapped
peripheral else when peripherals are located in memory space, they are called
Memory Mapped peripherals or memory mapped I/O.
xIf given a choice, Memory mapped peripherals are better because it has
advantages for both the hardware and software developers. It is attractive to
the hardware developer because he might be able to eliminate the I/O space,
and some of its associated wires, altogether. It is attractive to the software
developer who is able to use pointers, data structures, and unions to interact
with the peripherals more easily and efficiently.
5.3 Memory Map
xA Memory Map is the processor's "address book." It shows what these
devices look like to the processor. The memory map contains one entry for
each of the memories and peripherals that are accessible from the processor's
memory space.
xAll processors store their programs and data in memory.
xThese chips are loc ated in the processor's memory space, and the processor
communicates with them by way of two sets of electrical wires called the
address bus and the data bus. To read or write a particular location in memory,
the processor first writes the desired address onto the address bus. The data
is then transferred over the data bus.
xA memory map is a table that shows the name and address range of each
memory device and peripheral that is located in the memory space.
xOrganize the table such that the lowest address is at the bottom and the
highest address is at the top. Each time a new device is added, add it to the
memory map, place it in its approximate location in memory and label the
starting and ending addresses, i n hexadecimal. After inserting all of the
devices into the memory map, be sure to label any unused memory regions
as such.
xThe block diagram of the Printer sharing device shown above contains three
devices attached to the address and data buses. These de vices are the RAM
and ROM and a Serial Controller.
xLet us assume that the RAM is located at the bottom of memory and extends
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46INTRODUCTION TO EMBEDDED SYSTEMS
xThe ROM is located at the top of memory and extends downward for 256
KB. But c onsidering the ROM contains two ROMs -an EPROM and a Flash
memory device -each of size 128 KB.
xThe third device, the Serial Controller, is a memory -mapped peripheral
whose registers are accessible between the addresses say 70000h and 72000h.
xThe diagram below shows the memory map for the printer sharing device.

FFFFFh E0000h

C0000h 72000h
7000h

20000h



00000h


xFor every embedded system, a header file should be created
that describes these important features and provides an abstract interface to
the hardware. It allows the programmer to refer to the various devices on the
board by name, rather than by address.
xThe part of the header file below describes the me mory map
#define RAM_BASE (void *) 0x00000000 #define SC_BASE (void *) 0x70000000 #define SC_INTACK (void *) 0x70001000 #define FLASH_BASE (void *) 0xC0000000 #define EPROM_BASE (void *)
0xE0000000
5.4 I/O MAP
xThe I/O map contains one entry for each of the peripheral.
xAn I/O map has to be created if a separate I/O space is present. It is done by
repeating the steps performed to create memory map.
xTo create an I/O map, simply create a table of peripheral names and address
ranges, organized in such a way that the lowest addresses are at the bottom.
xThe diagram below shows the I/O map for the printer sharing device EPROM (128K) FLASH MEMORY
(128K) UNUSED SERIAL CONTROLLER UNUSED RAM (128K) munotes.in

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47Chapter 5: Embedded Hardware
FFFFh


FF00h

FE00h

FD00h FC00h


0000h

xIt includes three devices: the peripheral control block (PCB), parallel port,
and debugger port. The PCB is a set of registers within the processor that are
used to control the on -chip peripherals. The chips that control the parallel
port and debugger port reside outside of the processor. These ports are used
to communicate with the printer and a host -based debugger, respectively.
xThe part of the header file below describes the I/O map #define
SVIEW_BASE 0xFC00
#define PIO_B ASE 0xFD00 #define PCB_BASE 0xFF00
5.5 Interrupt Map
xThere are two techniques which can be used by the processor to communicate
with memories or peripheral devices. These are:
a. Polling : In this technique the processor polls the device (asks question)
repeatedly at regular intervals to check if the device has completed the
given task or has any new task to execute.
b. Interrupt: In interrupt, the device notices the CPU that it requires its
attention.
xAn interrupt is a signal sent from a peri pheral to the processor. A peripheral
may send an interrupt signal to a processor when it has some job to perform
which requires the processors intervention.
xUpon receiving an interrupt signal the Processor does the job by issuing
certain commands and wa its for another interrupt to signal the completion of
the job.
Peripheral
Control
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48INTRODUCTION TO EMBEDDED SYSTEMS
xWhile the processor is waiting for the interrupt to arrive, it is free to continue
working on other things.
xWhen a fresh interrupt signal is received, the processor temporarily sets aside
its current work and executes a small piece of software called the interrupt
service routine (ISR). When the ISR completes, the processor returns to the
work that was interrupted.
xThe programmer must write the ISR himself and enable it so that it will be
executed when the relevant interrupt occurs.
xInterrupt Map
xEmbedded systems usually have only a handful of interrupts. Associated with
each of these are an interrupt pin which is present on the outside of the
processor chip and an ISR.
xIn ord er for the processor to execute the correct ISR, a mapping must exist
between interrupt pins and ISRs. This mapping usually takes the form of an
interrupt vector table.
xThe vector table is usually just an array of pointers to functions, located at
some k nown memory address. The processor uses the interrupt type (a unique
number associated with each interrupt pin) as its index into this array. The
value stored at that location in the vector table is usually just the address of
the ISR to be executed.
xAn Interrupt Map is a step taken in this process. The Interrupt Map is a table
that contains a list of interrupt types and the devices to which they refer.
xThe diagram below shows the Interrupt map for the printer sharing device Interrupt Type Generating Device 8 Timer/Counter #0 17 Serial Controller 18 Timer/Counter #1 19 Timer/Counter #2 20 Serial Port Receive 21 Serial Port Transmit munotes.in

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49Chapter 5: Embedded Hardware
xOnce the I/O map is created the header file should be appended with the
following information:
#define SCC_INT 17 /*Serial Controller*/
#define TIMER0_INT 8 /* On -Chip Timer/Counters*/ #define
TIMER1_INT 18
#define TIMER2_INT 19
#define RX_INT 20 /* On -Chip Serial Ports */ #define TX_INT 21

5.6 Review Questions
1. Explain the Components involved in a printer sharing device
2. Explain Memory Map for a printer sharing device
3. Explain I/O Map for a printer sharing device
4. Explain interrupt Map for a printer sharing device

5.7 References & Further Reading
1. Programming Embedded systems in C++ by Michael Barr
2. Introduction to Embedded systems – Shibu K. V

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50INTRODUCTION TO EMBEDDED SYSTEMS
50Unit 2
6A EMBEDDED SYSTEMS: MEMORY
Unit Structure
6A.1 Objectives
6A.2 Introduction
6A.3 Types of Memory
6A.4 Types of RAM
6A.4.1 SRAM
6A 4.2 DRAM
6A.5 Types of ROM
6A.5.1 MASKED
6A.5.2 PROM
6A.5.3 EPROM
6A.6 Types of Hybrid Memory
6A.6.1 NVRAM
6A.6.2 FLASH
6A.6.3 EEPROM
6A.7 DIRECT MEMORY ACCESS (DMA)
6A.8 Review Questions
6A.9 References & Further Reading
6A.1 Objectives
After reading this chapter you will understand:
x Different types of memory available
x Types of RAM
x Types of ROM
x Types of Hybrid Memory
6A.2 Introduction
There are different types of memories available to be used in computers as well as
embedded system.
This chapter guides the reader through the different types of memories that are
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51Chapter 6A: Embedded Systems: Memory
6A.3 Types of Memory
xThere are three main types of memories, they are
a) RAM (Random Access Memory)
xIt is read write memory.
xData at any memory location can be read or written.
xIt is volatile memory, i.e. retains the contents as long as electricity is
supplied.
xData access to RAM is very fast
b) Rom (Read Only Memory )
xIt is read only memory.
xData at any memory location can be only read.
xIt is non -volatile memory, i.e. the contents are retained even after
electricity is switched off and available after it is switched on.
xData access to ROM is slow compared to RAM
c) Hybrid
xIt is combination of RAM as well as ROM
xIt has certain featu res of RAM and some of ROM
xLike RAM the contents to hybrid memory can be read and written
xLike ROM the contents of hybrid memory are non volatile

xThe following figure gives a classification of different types of memory

DRAM SRAM NVRAM Flash EEPROM EPROM PROM Masked
Figure: Types of Memor y
R O M
H y b r i d
R A M
M e m o ry
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52INTRODUCTION TO EMBEDDED SYSTEMS 6A.4 Types Of RAM
xThere are 2 important memory device in the RAM family.
d) SRAM (Static RAM)
e) DRAM (Dynamic RAM)
6A.4.1 SRAM (Static RAM)
f) It retains the content as long as the power is applied to the chip.
g) If the power is turned off then its contents will be lost forever.
6A.4.2 DRAM (Dynamic RAM)
a) DRAM has extremely short Data lifetime(usually less than a quarter of
second). This is true even when power is applied constantly.
b) A DRAM controller is used to make DRAM behave more like SRAM.
c) The DRAM controller periodically refreshes the data stored in the
DRAM. By refreshing the data several times, a second, the DRAM
controller keeps the contents of memory alive for a long time.
6A.5 Types Of Rom
There are three types of ROM described as follows:
6A.5.1 Masked ROM
a. These are hardwired memory devices found on system.
b. It contains pre-programmed set of instruction and data and it cannot be
modified or appended in any way. (it is just like an Audio CD that
contains songs pre -written on it and does not allow to write any other
data)
c. The main advantage of masked ROM is low cost of production .
6A.5.2 PROM (Programmable ROM )
a) This memory device comes in an un-programmed state
i.e. at the time of purchased it is in an un -programmed state and it allows the
user to write his/her own program or code into this ROM.
b) In the un -programmed state, the data is entirely made up of 1’s.
c) PROMs are also known as one -time-programmable (OTP) device
because any data can be written on it only once. If the data on the chip
has some error and needs to be modified this memory chip has to be
discarded and the modified data has to be written to another new
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53Chapter 6A: Embedded Systems: Memory 6A.5.3 EPROM (Erasable -And-Programable Rom)
a) It is same as PROM and is programmed in same manner as a PROM.
b) It can be erased and reprogrammed repeatedly as the name suggests.
c) The erase operation in case of an EPROM is performed by exposing
the chip to a source of ultraviolet light.
d) The reprogramming ability makes EPROM as essential part of
software development and testing process .
6A.6 Types of Hybrid Memory
There are three types of Hybrid memory devices:
6A.6. 1 EEPROMS
a. EEPROMs stand for Electrically Erasable and Programmable ROM.
b. It is same as EPROM, but the erase operation is performed electrically.
c. Any byte in EEPROM can be erased and rewritten as desired
6A.6.2 Flash
a. Flash memory is the most recent advancement in memory technology.
b. Flash memory devices are high density, low cost, nonvolatile, fast (to
read, but not to write), and electrically reprogrammable.
c. Flash is much more popular than EEPROM and is rapidly displacing
many of the ROM device s.
d. Flash devices can be erased only one sector at a time, not byte by byte.
6A.6.3 NVRAM
a. NVRAM is usually just a SRAM with battery backup.
b. When power is turned on, the NVRAM operates just like any other
SRAM but when power is off, the NVRAM draws enough electrical
power from the battery to retain its content.
c. NVRAM is fairly common in embedded systems.
d. It is more expensive than SRAM.
6A.7 Direct Memory Access ( DMA )
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54INTRODUCTION TO EMBEDDED SYSTEMS
ƒIn the absence of DMA the processor must read the data from one device and
write it to the other one byte or word at a time.
ƒDMA Absence Disadvantage: If the amount of data to be transferred is large
or frequency of transfer is high the rest of the software might never get a
chance to run.
ƒDMA Presence Advantage: The DMA Controller performs entire transfer
with little help from the Processor.
ƒWorking of DMA
ƒThe Processor provides the DMA Control ler with source and destination
address & total number of bytes of the block of data which needs transfer.
ƒAfter copying each byte each address is incremented & remaining bytes are
reduced by one.
ƒWhen number of bytes reaches zeros the block transfer ends & DMA
Controller sends an Interrupt to Processor.

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55Chapter 6A: Embedded Systems: Memory

6A.8 Review Questions
1. What are the different types of Memory?
2. What are the different types of RAM?
3. What are the different types of ROM?
4. What are the different types of Hybrid Memory?
6A.9 References & Further Reading
1. Programming Embedded systems in C++ by Michael Barr
2. Introduction to Embedded systems – Shibu K. V

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56INTRODUCTION TO EMBEDDED SYSTEMS
56 0 Unit 2
6B EMBEDDED SYSTEMS: MEMORY TESTING
Unit Structure
6B.1 Objectives
6B.2 Introduction
6B.3 Memory Testing and its purpose
6B.4 Common Memory Problems
6B.5 A strategy for memory testing
6B.5.1 Data Bus Test
6B.5.2 Address Bus Test
6B.5.3 Device Test
6B.6 Review Questions
6B.7 References & Further Reading
6B.1 Objectives
After reading this chapter you will be able to understand:
9What is memory testing?
9What are the common memory related problems?
9What are the different types of test to detect memory related problems and a
general idea about the working of these tests
6B.2 Introduction
The previous chapter dealt with the different types of memory. This chapter will
focus on the concept of testing memory devices, its purpose and different methods
available.
6B.3 Memory Testing and Its Purpose
xThe purpose of a memory test is to confirm that each storage location in a
memory device is working.
xMemory Testing is performed when prototype hardware is ready and the
designer needs to verify that address and data lines are correctly wired and
memory chips are working properly.
xBasic idea implement in testing can be understood by this simple task: munotes.in

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57Chapter 6B: Embedded Systems: Memory Testing 0 ƒWrite some set of Data va lues to each Address in Memory and Read it back
to verify.
ƒEx. If number ’50’ is stored at a particular Address it is expected to be there
unless rewritten or erased.
ƒIf all values are verified by reading back then Memory device passes the
test.
xOnly through careful selection of data values can make sure passing result
to be meaningful.
xDifficulties involved in memory testing:
ƒIt can be difficult to detect all memory problems with a simple test.
ƒMany Embedded Systems include Memory Tests only to detect catastrophic
memory failures which might not even notice memory chips removal.
6B.4 Common Memory Problems
ƒMemory Problems rarely occur with the chip itself, but due to a variety of
post-production tests to check quality this possibility i s ruled out.
ƒCatastrophic Failure is a memory problem that occurs due to physical and
electrical damage, it is uncommon and easily detectable.
ƒA common source of memory problems is associated with the circuit board.
Typical circuit board problems are:
1. Circuit board wiring between Processor & Memory device.
2. Missing Memory chip.
3. Improperly inserted Memory chip.
1. Circuit board wiring between Processor & Memory device.
ƒThese are usually caused by,
i. An error in design
ii. An error in production of the board
iii. Any damage after manufacture
ƒWires that connect the memory are:-
i. Address line :- select the memory location
ii. Data line :- transfer the data
iii. Control line :- read or write operation
ƒTwo wiring problems are shown below
1. Connected to another wire on the board
- May be caused by a bit of solder splash
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58INTRODUCTION TO EMBEDDED SYSTEMS 0 2. Not connected to anything
- Caused by broken trace


Figure: a. wiring problems: two wires shorted
b. wiring problems: one wire open
‡ When Address line has a wiring problem
Rmemory locations overlap
Ri.e. memory device to see an address different from the one selected
by the processor.
RProblem is with a data line
Rseveral data bits “stuck together”
Ri.e. two or more bits always contains same value
‡ When the problem is with a Data line
Rseveral data bits “stuck together”
Ri.e. two or more bits always contains same value
RWhen Control lines is shorted or open
‡ When Control lines is shorted or open
RThe operation of many control lines is specific to the processor or
memory architecture.
Rthe memory will probably not work at all.


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59Chapter 6B: Embedded Systems: Memory Testing 0 2. Missing Memory chip.
RA missing memory chip is clearly a problem that should be detected
RUnfortunately, because of the capacitive nature of unconnected electrical wires, some memory tests will not detect.
RFor e.g. suppose you decided to use the following test algorithm
9write the value 1 to the first location in memory, verify the
value by reading it back
9write 2 to the second location, verify the value
9write 3 to the third location, verify, etc.
RBecause each read occurs immediately after the corresponding write, it
is possible that the data read back represents nothing more than the
voltage remaining on the data bus from th e previous write.
RIf the data is read back too quickly, it will appear that the data has been
correctly stored in memory -even though there is no memory chip at the
other end of the bus!
RTo detect a missing memory chip the previous algorithm for test must
be altered.
RFor example,
9write the value 1 to the first location,
92 to the second location,
9And 3 to the third location,
RThen verify the data at the first location, the second location, etc. If the
data values are unique (as they are in the test just described), the
missing chip will be detected
3. Improperly inserted Memory chip.
ƒCaused by pins on the memory chip
RWill either not be connected to the socket at all
RWill be connected at the wrong place
ƒSymptoms: -
RSystem behaves same as though there is a wiring problem or a
missing chip.
ƒHow to detect :-
RDetected by any test
6B.5 A Strategy For Memory Testing
xFor memory testing the strategy adopted should be effective and efficient.
Ideally there should be multiple small tests instead of one large test.
xIt would be best to have three individual memory tests:
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60INTRODUCTION TO EMBEDDED SYSTEMS 0 3. A device test: Checks to detect missing chips and catastrophic failures and
problems with the control bus wiring
xThese tests have to be executed in a proper order which is: data bus test first,
followed by the address bus test, and then the device test. That's because the
address bus test assumes a working data bus, and the device test results are
meaningless unless both the address and data buses are known to be good.
6B.5.1 Data Bus Test
xIt is used to check data bus wiring.
xIn this test we need to confirm that the received data is same as the data sent
by processor
xImplementation:
ƒHere we write all possible data values and verify that the memory device
stores each one successfully.
ƒIn short to test the bus one bit at a time.
xWalking 1's test
ƒThis test is used to independently test every bit.
ƒA single data bit is set to 1 and “walked” through the entire data word.
ƒIf the data bus is working properly, the function will return 0.
ƒOtherwise it will return the data value for which the test failed.
ƒBecause we are testing only the data bus at this point, all of the data values
can be written to the same address. Any address within the memory device
will do
00000001
00000010
00000100
00001000
00010000
00100000
01000000
10000000
Figure: Consecutive data values for walking 1's test
6B.5.2 Address Bus Test
xAddress bus problems lead to overlapping memory locations.
xIn the Address Bus test we need to confirm that each of the address pins can
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61Chapter 6B: Embedded Systems: Memory Testing 0 xThe smallest set of address that will cover all possible combinations is the set
of “power of two” addresses.
xAfter writing one of the addresses, we must check none of the others has been
overwritten.
6B.5.3 Device Test
xIt is used to test if the memory device is working properly. It is necessary to
test the integrity of the memory device itself.
xThe thing to test is that every bit in the device is capable of holding both 0
and 1.
xFor a thorough and complete device test every memory location has to be
visited twice.
xA simple test implemented is the Increment test as shown in the table
below
¾The first column represents the memory location
¾The second column represents the data that is written at the memory
location indicated in column 1 in incremental fashion.
¾The third column represents the data of column 2 in inverted format.

Figure: Data Bus Test – Increment Test
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62INTRODUCTION TO EMBEDDED SYSTEMS 0 xDuring the first pass the data in column 1 is verified and during second pass
the data in column 2 is verified.
6B.6 Review Questions
1. What is Memory Testing? Why is it required?
2. What are common memory problems in embedded system?
3. Describe a test strategy for performing memory testing on embedded system.
Is there a specific order to perform these tests? if yes, why?
4. Describe the different types of memory testing techniques available.
6B.7 References & Further Reading
1. Programming Embedded systems in C++ by Michael Barr
2. Introduction to Embedded systems – Shibu K. V

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63Chapter 7: Embedded Systems: Peripherals
63 0 Unit 2
7 EMBEDDED SYSTEMS: PERIPHERALS
Unit Structure
7.1 Objectives
7.2 Introduction
7.3 Testing Non Volatile Memory Devices
7.4 Control and Status Registers
7.5 Device Driver
7.6 Watchdog timer
7.7 Review Questions
7.8 References & Further Reading
7.1 Objectives
After reading this chapter you will learn:
5.7.1 Concept of testing non –volatile memory devices using Checksum and CRC
5.7.2 Control and Status Registers
5.7.3 Device Driver
5.7.4 Watch Dog Timer
7.2 Introduction
This chapter initially continues the part of memory testing from last chapter. Here
testing of Non Volatile memory devices is studied.
Then we study how peripheral devices are incorporated in Embedded System.
Control and Status Registers, Devi ce Drivers and Watch Dog Timers are explained
in the subsequent sections.
7.3 Testing Non Volatile (Rom And Hybrid) Memory Devices
xThe testing techniques described previously cannot help to test ROM and
hybrid devices since ROM devices cannot be written at all, and hybrid
devices usually contain data or programs that cannot be overwritten.
xHowever, ROM or hybrid memory device face the same problems as missing
memory chip, improperly inserted memory chip, damaged memory chip or
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64INTRODUCTION TO EMBEDDED SYSTEMS 0 xTwo Techniques Checksums and CRC can be used to test non volatile
memory devices.
xChecksum
¾Checksums basically deals with the question whether the data stored in
a memory device is valid or not?
¾To do this the checksum of the data in the memory device is computed
and stored along with the data. The moment when we have to confirm
the validity of the data, we just have to recalculate the checksum and
compare it with previous checksum. If the two checksums match, the
data is assumed to be valid.
¾The simplest checksum algorithm is to add up all the data bytes
discarding carries.
¾A Ch ecksum is usually stored at some fixed location in memory. This
makes it easy to compute and store the check sum for the very first time
and later on to compare the recomputed checksum with the original
one.
¾Disadvantage: A simple sum -of-data checksum ca nnot detect many of
the most common data errors.
xCRC – Cyclic Redundancy Check
¾A Cyclic Redundancy Check is a specific checksum algorithm designed to detect the most common data errors.
¾CRC’s are frequently used in Embedded Applications that requires the
storage or transmission of large blocks of data.
¾The CRC works as follows:
‰The message is composed of a long string of 0’s and 1’s
‰A division operation occurs between the message at numerator and the
generator polynomial at denominator. The generator polynomial is a
fixed smaller length binary string.
‰The remainder of the division operation is the CRC Checksum
7.4 Control and Status Registers
x Control and status registers are the basic interface between and embedded
processor and peripheral device.
x These registers are a part of peripheral hardware and their location size and
individual meanings are feature of the peripheral.
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65Chapter 7: Embedded Systems: Peripherals 0 x For example, the registers vary from device to device: example the registers
within a serial controller are very different from those in a timer.
x Depending upon the design of the processor and target board , peripheral
devices are located either in the processor’s memory space or within the I/O
space.
x It is common for Embedded Systems to in clude some peripherals of each type.
These are called Memory -Mapped and I/O -mapped peripherals.
x Of the two types, memory -mapped peripherals are generally easier to work
with and are increasingly popular.
x Memory -mapped control and status registers can be used just like ordinary
variables.
7.5 Device Driver
x The goal of designing a device driver is to hide the hardware completely.
x Attempts to hide the hardware completely are difficult.
x For example, all Flash memory devices share the concept of sectors. An erase
operation can be performed only on an entire sector. Once erased individual
bites or words can be rewritten.
x Device drivers for embedded systems are quite different from the workstation
counter parts. In modern computers workstation device drivers are most often
concerned with satisfying the requirement of the operating system.
x There are three benefits of good device driver:
i. Modularization, it makes the structure of the overall software is easier
to understand.
ii. There exists only one module that interacts directly with the
peripheral’s registers making communication easier.
iii. Software changes that result from hardware changes are localized to
the device driver.
Components o f a Device Driver
A device driver can be implemented (as components) in the following steps:
1. A data structure that overlays the memory -mapped control and status
registers of the device:
ƒThis basic step involves creating a C style structure that is actually a
map of the registers present in the device. These registers can be found
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66INTRODUCTION TO EMBEDDED SYSTEMS 0 ƒA table is created which maps the control register to their relative
offsets.
ƒAn example is shown below for a timer c ounter data structure.

struct TimerCounter
{
unsigned short count; // Current Count, offset 0x00 unsigned short maxCountA;//
Maximum Count, offset 0x02 unsigned short _reserved; // Unused Space, offset
0x04 unsigned short control; // Control Bits, offset 0x06
};
ƒTo make the bits within the control register easier to read and write
individually, we define the following bitmasks:
#define TIMER_ENABLE 0xC000 // Enable the timer.
#define TIMER_DISABLE 0x4000 // Disable the timer.
#define TIMER_INTERRUPT 0x2000 // Enable timer interrupts.
#define TIMER_MAXCOUNT 0x0020 // Timer complete?
#define TIMER_PERIODIC 0x0001 // Periodic timer?
2. A set of variables to track the current state of the hardware and device
driver: It involves listing out the required variables needed to keep track of
the state of the hardware and device driver
3. Initialize the hardware: Once the variables to be used are known the next step in device driver programming is to initialize the hardware. Next functions can be written to control the device.
4. A set of routines that provide an API for users of the device driver
This involves writing different functions that will implement the various
tasks listed to be performed by the device.
5. Interrupt serv ice routines
Once the required functions and routines are coded the thing remaining to be
done is to identify and write routines for servicing the interrupts.
7.6 Watchdog Timer
¾It is hardware equipment.
¾It is special purpose hardware that protects th e system from software hangs.
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67Chapter 7: Embedded Systems: Peripherals 0 ¾This process takes a few seconds to reset, in the meantime, it is possible for
embedded software to “kick” the watchdog timer, to reset its counter to the
original large number.
¾If the timer expires i.e. counter reaches zero, the watchdog timer will assume
that the system has entered a state of software hang, then resets the embedded
processor and restarts the software
¾It is a common way to recover from unexpected software hangs
¾The figure below diagrammatically represents the working of the watchdog
timer

Figure: Watchdog Timer
7.7 Review Questions
1. Explain testing for non -volatile memory devices
2. Write short note on Control and status registers
3. What is a device driver?
4. What are the components of a device driver?
5. Write short note on Watch Dog Timer
7.8 References & Further Reading
1. Programming Embedded systems in C++ by Michael Barr
2. Introduction to Embedded systems – Shibu K. V

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68 Unit 3
8 THE 8051 MICROCONTROLLERS
Unit Structure
8.0 Objectives
8.1 Introduction
8.2 An Overview
8.3 Microcontroller and Embedded Processors
8.3.1 Processors in System
8.3.2 Types of Processors
8.3.3 Microprocessor Vs Microcontroller
8.4 Overview of 8051 Family
8.4.1 Brief History of 8051
8.4.2 8051 Members
8.4.3 Comparison Between 8051 family Members
8.4.4 Features of 8051 Microcontroller
8.5 8051 Microcontroller Hardware
8.5.1 Block Diagram of 8051 Microcontroller
8.5.2 Applications of 8051 Microcontroller
8.6 Input/output Pins, Ports, and Circuits,
8.7 External Memory
8.8 Summary
8.9 Review Questions
8.10 References & Further reading
8.0 Objectives
To know the all-Basic things about Microcontroller , Microprocessor (Embedded)
& family . How we use Microcontroller & Its Applications in various fields .
To study how we select Microcontroller. To study of Memories & Data conversion
useful in Microcontroller. It can be thought of as a computer hardware system
having software embedded in it. An embedded system can be either an independent
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8.1 Introduction
As we know an embedded system as a microcontroller -based, software -driven,
reliable, real -time control system, designed to perform a specific task. A printer is
an example of embedded system since the processor inside it performs only one
task namely, gett ing the data and printing it. An embedded product uses a
microprocessor (or microcontroller) to do one task only.
PC can be used for any number of applications such as word processor, print server,
bank teller terminal, video game player, network server, o r internet terminal.
Software for a variety of applications can be loaded and run. PC can perform
myriad tasks is that it has RAM memory and an operating system that loads the
application software into RAM and lets the CPU run it.
8051 is one of the first most popular microcontroller also known as MCS -51. It
introduced it in the year 1981 by Intel Company . The 8051 Microcontroller is one
of the most popular general purpose microcontrollers especially designed for
embedded systems. It a small chip based on an architecture with support for
embedded applications, such as measuring device, security systems, robotics,
remoter control applications, scroll message display, etc.
8.2 An Overview Whatever we make, using Microcontroller that is also possible with Microprocessor, but main thing is cost & Size (Microcontroller implied with
compact size & low cost). A system is an arrangement in which all its unit assemble
& work tog ether according to protocols . It can also be defined as a way of working,
organizing or doing one or many tasks according to a fixed plan. For example, a
watch is a time displaying system. Its components follow a set of rules to show
time. If one of its parts fails, the watch will stop working. Therefore, we can say in
a system, all its subcomponents depend on each other.
As its name suggests, Embedded means something that is attached to another thing.
An embedded system can be thought of as a computer hardware system having
software embedded in it. An embedded system can be an independent system or it
can be a part of a large system. An embedded system is a microcontroller or
Microprocessor based system, which is designed to perform a specific task.
8.3 Microcontroller and Embedded Processors
8.3.1 Processors in a System
A processor has two essential units -
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The CU includes a fetch unit for fetching instructions from the memory. The EU
has circuits that implement the instructions pertaining to data transfer operation and
data conversion from one form to another.
The EU includes the Arithmet ic and Logical Unit (ALU) and the circuits that
execute instructions for a program control task such as interrupt or jump to another
set of instructions.
A processor runs the cycles of fetch and executes the instructions in the same
sequence as they are fetched from memory.
8.3.2 Types of Processors
General Purpose Processor (GPP) can be of the following categories -
RMicroprocessor
RMicrocontroller
REmbedded Processor
RDigital Signal Processor
RMedia Processor
Microprocessor:
A microprocessor is a single VLSI chip having a CPU. In addition, it may also have
other units such as coaches, floating -point processing arithmetic unit, and pipelining units that help in faster processing of instructions. Earlier generation
microprocesso rs’ fetch -and-execute cycle was guided by a clock frequency of order
of ~1 MHz Processors now operate at a clock frequency of 2GHz .

Block Diagram of General purpose Microprocessor
Microcontroller:
A microcontroller is a single -chip VLSI unit (also called microcomputer) which, although having limited computational capabilities, possesses enhanced input/output capability and a number of on -chip functional units.

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71Chapter 8: The 8051 MicrocontrollersCPU RAM ROM I/O Port Timer Serial COM Port Block Diagram of Basic Microcontroller
Microcontrollers are particularly used in embedded systems for real -time control
applications with on -chip program memory and devices.
Embedded Processor
Embedded processor is a type of microprocessor designed into a system to control
electrical and mechanical functions. Embedded processors are usually simple in
design, limited in computational power, I/O capabilities, and have minimal power
requirements. At a basic level, embedded processors are a CPU chip placed in a
system th at it helps control.
Digital Signal Processor
Digital signal processing (DSP ) is the use of digital processing , such as by
computers or more specialized digital signal processors , to perform a wide variety
of signal processing operations.
Media processor
A media processor, mostly used as an image/video processor, is a microprocessor -
based system -on-a-chip which is designed to deal with digital streaming data in
real-time (e.g. display refresh) rates.
8.3.3 Microprocessor Vs Microcontroller
Let us now take a look at the most notable difference between a microprocessor
and a microcontroller. Microprocessor Microcontroller Microprocessors are multitasking in nature. Can perform multiple tasks at a
time.
For example, on computer we can play
music while writing text in text editor. Special purpose & Single task oriented.
For example, a washing machine is
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72INTRODUCTION TO EMBEDDED SYSTEMSDesigner must add RAM, ROM, I/O Ports, and Timers externally . RAM, ROM, I/O Ports, and Timers components embedded together OR
inbuilt on a chip. Designers can decide the number of memory or I/O ports needed. Fixed number for memory or I/O makes a microcontroller ideal for a
limited but specific task. External support of external memory and I/O ports makes a microprocessor -based
system heavi er and costlier. Microcontrollers are lightweight and cheaper than a microprocessor. External devices require more space and their power consumption is higher. A microcontroller-based system consumes less power and takes less
space / compact size .
8.4 Overview of 8051 Family
8.4.1 Brief History Of 8051
In 1981, Intel Corporation introduced an 8-bit microcontroller called the 8051.
This microcontroller had 128 bytes of RAM, 4K bytes of on -chip ROM, two timers,
one serial port, and four ports (each 8 -bits wide) all on a single chip. At the time, it
was also referred to as a “system on a chip.” The 8051 is an 8 -bit pr ocessor,
meaning that the CPU can work on only 8 bits of data at a time. Data larger than 8
bits has to be broken into 8 -bit pieces to be processed by the CPU. The 8051 has
four I/O ports, each 8 bits wide. See Figure 1 -2. Although the 8051 can have a
maxi mum of 64K bytes of on -chip ROM, many manufacturers have put only 4K
bytes on the chip. This will be discussed in more detail later.
8.4.2 8051 Members
x8052 microcontroller -8052 has all the standard features of the 8051 microcontroller as well as an extra 128 bytes of RAM and an extra timer. It
also has 8K bytes of on -chip program ROM instead of 4K bytes.
x8031 microcontroller -It is another member of the 8051 family. This chip is
often referred to as a ROM -less 8051, since it has 0K byte of on -chip ROM.
You must add external ROM to it in order to use it, which contains the
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bytes. However, in the pro cess of adding external ROM to the 8031, it lost
two ports out of 4 ports. To solve this problem, we can add an external I/O to
the 8031 .
8.4.3 Comparison between 8051 Family Members
The following table compares the features available in 8051, 8052, and 8031. Feature 8051 8052 8031 ROM(bytes) 4K 8K 0K RAM(bytes) 128 256 128 Timers 2 3 2 I/O pins 32 32 32 Serial port 1 1 1 Interrupt sources 6 8 6
8.4.4 Features of 8051 Microcontroller
An 8051 microcontroller comes bundled with the following features -
x8 Bit microcontroller
x40 Pins DIP (Dual In package)
x4KB bytes on -chip program memory (ROM)
x128 bytes on -chip data memory (RAM)
xFour register banks
x128 user defined software flags
x8-bit bidirectional data bus
x16-bit unidirectional address bus
x32 general purpose registers each of 8 -bit
x16 bit Timers (usually 2, but may have more or less)
xThree internal and two external Interrupts
xFour 8 -bit ports , (short model have two 8 -bit ports)
x16-bit program counter and data pointer
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8.5 The 8051 Microcontroller Hardware
8.5.1 Block Diagram of 8051 Microcontroller
The following illustration shows the block diagram of an 8051 microcontroller -
Central Processor Unit (CPU) As we know that, the CPU is the brain of any processing device of the microcontroller. It monitors and controls all operations that are performed on the
Microcontroller units. The user has no control over the work of the CPU directly.
It reads program written in ROM memory, executes them, and do the expected task
of that application.

Fig. 8051 Microcontroller Architecture
Interrupts
As its name suggests, Interrupt is a subroutine call that interrupts of the microcontrollers main operations or work and causes it to execute any other program , which is more important at the time of operation. The feature of
Interrupt is very useful as it helps in case of emergency operations. An Interrupts
gives us a mechanism to put on hold the ongoing operations, execute a subroutine
and then again resumes to another type of operations.
The Microcontroller 8051 can be configured in such a way that it temporarily
terminates or pause the main program at the occurrence of interrupts. When a
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subroutine is completed, then the execution of main program starts. Generally five
interrupt sources are there in 8051 Microcontroller.
There are 5 vectored interrupts are shown in below
xINTO
xTFO
xINT1
xTF1
xR1/T1
Memory
Micro controller requires a program, which is a collection of instructions. This
program tells microcontroller to do specific tasks. These programs require a
memory on which these can be saved and read by Microcontroller to perform
specific operations of a parti cular task. The memory which is used to store
the program of the microcontroller is known as code memory or Program memory
of applications. It is known, as ROM memory of microcontroller also requires a
memory to store data or operands temporarily of the micro controller. The data
memory of the 8051 is used to store data temporarily for operation is known RA M
memory. 8051 microcontrollers has 4K o f code memory or program memory
that has 4KB ROM and 128 bytes of data memory of RAM.
Bus
Bus is a collection of wires, which work as a communication channel or medium
for transfer of Data. These buses consist of 8, 16 or more wires of the microcontroller. Thus, these can carry 8 bits, 16 bits simultaneously. Hire two types
of buses that are as follows :
xAddress Bus
xData Bus
Address Bus : Microcontroller 8051 has a 16-bit address bus for transferring the
data. It is used to address memory locations and to transfer the address from CPU
to Memory of the microcontroller. It has four addressing modes that are
Data Bus : Microcontroller 8051 has 8 bits of the data bus, which is used to carry
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Oscillator
Generally, we know that the microcontroller is a device; therefore, it requires clock pulses for its operation of microcontroller applications. For this purpose, microcontroller 8051 has an on -chip oscillator that works as a clock source for
Central Processing Unit of the microco ntroller. The output pulses of oscillator are stable. Therefore, it enables synchronized work of all parts of the 8051 Microcontroller.
Input / Output Port
Normally microcontroller is used in embedded systems to control the operation of
machines in the microcon troller. Therefore, to connect it to other machines, devices
or peripherals we re quire I/O interfacing ports in the microcontroller interface. For
this purpose microcontroller 8051 has four input, output ports to connect it to the
other peripherals .
Timers/Counters
The 8051 microcontroller has two 16-bit timers and counters. These counters are
again divided into a n 8-bit register. The timers are used for measurement of
intervals to determine the pulse width of pulses.
8.5.2 Applications of 8051 Microcontroller
Some of the applications of 8051 is mainly used in daily life & industrial
applications some of those application s are shown below
xLight sensing and controlling devices
xTemperature sensing and controlling devices
xFire detections and safety devices
xAutomobile applications
xDefence applications
Some industrial applications of micro controller and its applications
xIndustrial instrumentation devices
xProcess control devices
Some of 8051 microcontroller devices are used in measurement applications
xVoltmeter applications
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8.6 Input/output Pins, Ports & Circuits
I/O Pins – Pin number Name of Pin Function 1 to 8 Port 1 Internally pulled up, Bidirectional I/O port 9 RESET pin To Reset Microcontroller to its initial values 10 to 17 Port 3 Interrupts, timer & control, serial communication 18, 19 Crystal Clock Interfacing external crystal to get system clock 20 Supply Power supply to the circuit 21 to 28 Port 2 I/O Port 29 PSEN Program Store Enable to read signal from External memory 30 EA External Access Input for External Memory interface 31 ALE Address Latch Enable to DE multiplex Address Data Bus / signal of port 32 to 39 Port 0 I/O port / Lower order address & data bus multiplexed 40 GND Complete the Circuit (To provide supply)
I/O Ports and Circuits :
Each port of 8051 has bidirectional capability. Port 0 is called 'true bidirectional
port' as it floats when configured as input. Port -1, 2, 3 are called 'quasi bidirectional
port’. Port -0 Pin Structure Port -0 has 8 pins (P0.0 -P0.7).

Fig. Port -0 Structure
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Port-0 can be configured as a normal bidirectional I/O port or it can be used for
address/data interfacing for accessing external memory. When control is '1', the
port is used for address/data interfacing. When the control is '0', the port can be
used as a normal bidirectional I/O port.
Let us assume that control is '0'. When the port is used as an input port, '1' is written
to the latch. In this situation both the output MOSFETs are 'off'. Hence the output
pin floats. This high impedance pin can be pulled up or low by an external source.
When the port is used as an output port, a '1' written to the latch again turns 'off'
both the output MOSFETs and causes the output pin to float. An external pull -up
is required to output a '1'. But when '0' is written to the latch, the pin is pulled down
by the lower MOSFET. Hence the output becomes zero.
When the control is '1', address/data bus controls the output driver MOSFETs. If
the address/data bus (internal) is '0', the upper MOSFET is 'off' and the lower
MOSFET is 'on'. The output becomes '0'. If the address/data bus is '1', the upper
transistor is 'on' and the lower transistor is 'off'. Hence the output is '1'. Hence for
normal address/data i nterfacing (for external memory access) no pull -up resistors
are required.
Port-0 latch is written to with 1's when used for external memory access.
Fig. Port -1 Structure
Port-1 does not have any alternate function i.e. it is dedicated solely for I/O
interfacing. When used as output port, the pin is pulled up or down through internal
pull-up. To use port -1 as input port, '1' has to be written to the latch. In this input
mode when '1' is written to the pin by the external device then it read fine. But when
'0' is written to the pin by the external device then the external source must sink
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current due to internal pull -up. If the external device is not able to sink the current
the pin voltage may rise, leading to a possible wrong reading.
Fig. Port -2 Structure
Port-2 is used for higher external address byte or a normal input/output port. The
I/O operation is similar to Port -1. Port -2 latch remains stable when Port -2 pin are
used for external memory access. Here again due to internal pull -up there is limited
current driving capability.

Fig. Port -3 Structure
Each pin of Port -3 can be individually programmed for I/O operation or for
alternate function. The alternate functi on can be activated only if the corresponding
latch has been written to '1'. To use the port as input port, '1' should be written to
the latch. This port also has internal pull -up and limited current driving capability.
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8.7 External Memory
The 8051 Microcontroller based on Harvard Architecture & Instructions / program
to be executed are stored in Internal Memory (4 KB ROM). Here Address space
available is 0000H to 0FFFH. If we want to connect External memory, address
range available from 1000H to FFF FH. (H indicates Hexadecimal address)
Interfacing External Memory :
If external program/data memory are to be interfaced, they are interfaced in the
following way.
Fig. Interfacing External Memory with 8051
External program memory is fetched if either of the following two conditions are
satisfied.
1. (Enable Address) is low. The microcontroller by default starts searching for
program from external program memory.
2. PC is higher than FFFH for 8051.
PSEN tells the outside world whether the external memory fetched is
program memory or data memory.
8.8 Summary
Embedded system as a microcontroller -based, software -driven, reliable, real -time
control system, designed to perform a specific task. In Microcontroller inbuilt
available RAM, ROM, I/O Ports and Timers etc. In many Applications Space,
Power, cost are much consideration so we prefer Microcontroller.
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The 8051 Microcontroller is 8 Bit, 40 Pins DIP. It is most popular so used in daily
life & industrial applications. In family of 8051 Microcontroller 2 more Microcontroller compatible as 8052 OR 8031 depends on Application as their
features are different. To Interface 2 or more devices for communication as
Input/output Pins, Ports, Circuits, External Memor y can add as Hardware of
Embedded that depends on Applications.
8.9 Review Questions
1) Give Overview of 8051 family
2) What are the requirements of 8051 Microcontroller Hardware?
3) Explain Microcontroller & Embedded processors.
4) Draw Block diagram of 8051 with important I/O Pins
5) How we interface External Memory to 8051
6) Give Ports & circuits of 8051.
7) Differentiate Microprocessor & Microcontroller
8) Give Applications of 8051
8.10 References & Further reading
1) Book Embedded Systems Architecture, Programming & Design (Second
Edition / The McGraw Hill publications ) by Raj kamal .
2) Introduction to Embedded system By Shibu K V (Tata McGraw Hill
Publications)
3) Book Embedded System by Ashwini Somnathe & Abhijit Somnathe for
SYBSc IT (Sheth Publications)

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82Unit 3
9 C - LANGUAGE
Unit Structure
9.0 Objectives
9.1 Introduction
9.2 An Overview
9.3 8051 Programming in C
9.3.1 Basics of Embedded C Program
9.3.2 Factors for Selecting the Programming Language
9.3.3 Difference between C and Embedded C
9.3.4 Keywords in Embedded C
9.4 Data Types and Time Delay in 8051 C
9.5 I/O Programming
9.5.1 Pin Diagram
9.5.2 I/O Ports and Their Functions
9.5.3 Hardware Connection of Pins
9.5.4 I/O Ports and Bit Addressability
9.5.5 Single -Bit Instructions
9.6 Logic Operations
9.6.1 Basics of Bitwise Operations
9.7 Data Conversion Programs
9.8 Summary
9.9 Questions
9.10 References & Future Reading
9.0 Objectives
To learn the different steps involved in the design & Development of C programming in Embedded system. Learn about the fundamentals of Programming, firmware using Embedded C. To study of Data Types and Time
Delay, I/O Programming, Logic Operations & Data Conversio n Programs in
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9.1 Introduction
Programming is the most essential part of any Embedded system. Programming is
required for Computational tasks. Program in a High level language gives us
benefits of short development cycle for a complex system hardware modifications.
C began to grow in popularity not just for systems programming, but as a general
purpose programming language.
The extension of the C language is called an Embedded C programming language.
The C programming language was originally developed as a language to replace
assembler in systems programming. It was very successful, making system code
portable and easier to write and read.
9.2 An Overview
Each processor is associated with embedded software. Embedded C
Programming plays a major role in performing specific functions by the processor.
In our day -to-day life, we frequently us e many electronic devices such as washing machines, mobile phones, digital camera and so on will work based on microcontrollers that are programmed by embedded C .
The C code written is more reliable, portable, scalable and much easier to
understand. The first and foremost tool is the embedded software that decides the
operation of an embedded system. Embedded C programming language is most
frequently used for programming the microcontrollers. For writing the pr ogram the
embedded designers must have sufficient knowledge on the hardware of particular
processors or controllers as the embedded C programming is a full hardware related
programming technique. The 8051 microcontroller is the 8-bit 'CISC' architecture.
It consists of memories, serial communication, interrupts, input/output ports and
timer/counters, built into a single integrated chip, which is programmed to control
the peripheral devices which are interfaced with it.
An example of Embedded system is a Car. A modern day Car has several individual
embedded systems that perform their specific tasks with the aim of making a
smooth and safe journey. Some of the embedded systems in a Car are Anti -lock
Braking System (ABS), Temperature Monitoring System, Automatic Climate
Control, Tire Pressure Monitoring System, Engine Oil Level Monitor, etc.
9.3 8051 Programming In C
9.3.1 Basics of Embedded C Program
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Embedded C. Embedded C is perhaps the most popular languages among Embedded Programmers for programming Embedded Systems. There are many
popular programming languages like Assembly, BASIC, C++, Python etc. that are
often used for developing Embedded Systems but Embedded C remains popular
due t o its efficiency, less development time and portability.
An Embedded System can be best described as a system, which has both the
hardware and software and is designe d to do a specific task. A good example for
an Embedded System, which many households a Washing Machine. It takes some
inputs from the user like wash cycle, type of clothes, extra soaking and rinsing, spin
rpm, etc., performs the necessary actions as per the instructions and finishes
washing and drying the clo thes. If no new instructions are given for the next wash,
then the washing machines repeats the same set of tasks as the previous wash.
Embedded Systems can not only be stand -alone devices like Washing Machines
but also be a part of a much larger system.
9.3.2 Factors for Selecting the Programming Language
The following are few factors that are to be considered while selecting the
Programming Language for the development of Embedded Systems.
xSize: The memory that the program occupies is very important as Embedded
Processors like Microcontrollers have a very limited amount of ROM
(Program Memory).
xSpeed : The programs must be very fast i.e., they must run as fast as possible.
The hardware should not be slowed down due to a slow running softwar e.
xPortability : The same program can be compiled for different processors.
xEase of Implementation
xEase of Maintenance
xReadability
9.3.3 Difference between C and Embedded C
C Language
xC used for desktop based applications
xC code generate the compatible .exe files
xIt has limitless resources like memory
xC language uses the desktop OS memory
xC don ’t have registers to store data temporarily
Embedded C:
xIt is used for micro controller based applications
xEmbedded programs generate the .hex files
xIt has limited resources like memory (RAM, ROM)
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9.3.4 Keywords in Embedded C
A Keyword is a special word with a special meaning to the compiler (a C Compiler
for example, is a software that is used to convert program written in C to Machine
Code).
Writing code
Example 1: Blinking of LED connected to Port 1 of 8051 .
Program:
#include
//delay function declaration
void delay(void);
void main(void)
{
//an infinite loop
while(1)
{
// Turn ON all LED's connected to Port1
P1 = 0xFF;
delay();
// Turn OFF all LED's connected to Port1
P1 = 0x00;
delay();
}
}
//delay function definition
void delay(void)
{
int i,j;
for(i=0;i<0xff ;i++)
for(j=0;j<0xff;j++);
}
Example 2: Write a program to generate a 10 KHz square wave using 8051.
Program:
#include
void main()
{
unsigned int x;
for(;;)
{
P1=0X80;
for(x=0;x<40000;x++)
{
P1=0X00;
}
}
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9.4 Data Types and Time Delay In 8051 C
Data Types :
Data Types in C Programming Language (or any programming language for that
matter) help us declaring variables in the program. There are many data types in C
Programming Language like signed int, unsigned int, signed char, unsigned char,
float, double, etc. In addition to these there few more data types in Embedded C.
The following are the extra data types in Embedded C associated with the Keil’s
Cx51 Compiler.
xbit
xsbit
xsfr
xsfr16
The following table shows some of the data types in Cx51 Compiler along with
their ranges. Data Type Bits (Bytes) Range Bit 1 0 or 1 (bit addressable part of RAM) signed int 16 (2) -32768 to +32767 unsigned int 16 (2) 0 to 65535 signed char 8 (1) -128 to +127 Unsigned 8 (1) 0 to 255 Float 32 (4) ±1.175494E-38 to ±3.402823E+38 Double 32 (4) ±1.175494E-38 to ±3.402823E+38 Sbit 1 0 or 1 (bit addressable part of RAM) Sfr 8 (1) RAM Addresses (80h to FFh) sfr16 16 (2) 0 to 65535
Time Delay :
The delay length in 8051 microcontroller depends on three factors:
The crystal frequency
The number of clock per machine
The C compiler.
Code generating delay using timer register:
#include
void T0Delay(void);
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while (1)
{
P1=0x55;
T0Delay();
P1=0xAA;
T0Delay();
}
}
void T0Delay(){
TMOD=0x01; // timer 0, mode 1
TL0=0x00; // load TL0
TH0=0x35; // load TH0
TR0=1; // turn on Timer0
while (TF0==0); // wait for TF0 to roll over
TR0=0; // turn off timer
TF0=0; // clear TF0
}
9.5 I/O Programming
9.5.1 Pin Diagram

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9.5.2 I/O Ports and Their Functions
The four ports P0, P1, P2, and P3, each use 8 pins, making them 8 -bit ports. Upon
RESET, all the ports are configured as inputs, ready to be used as input ports. When
the first 0 is written to a port, it becomes an output. To reconfigure it as an input, a
1 must be sent to a port.
Port 0 (Pin No 32 – Pin No 39)
It has 8 pins (32 to 39). It can be used for input or output. Unlike P1, P2, and P3
ports, we normally connect P0 to 10K -ohm pull -up resistors to use it as an input
or output port being an open drain.
It is also designated as AD0 -AD7, allowing it to be used as both address and data.
In case of 8031 ( i.e. ROM less Chip), when we need to access the external ROM,
then P0 will be used for both Address and Data Bus. ALE (Pin no 31) indicates if
P0 has address or data. When ALE = 0, it provides data D0 -D7, but when ALE =
1, it has address A0 -A7. In case no external memory connection is available, P0
must be connected externally to a 10K -ohm pull -up resistor.

MOV A,#0FFH ;(comments: A=FFH(Hexadecimal i.e. A=1111 1111)
MOV P0,A ;(Port0 have 1's on every pin so that it works as Input)
Port 1 (Pin 1 th rough 8)
It is an 8 -bit port (pin 1 through 8) and can be used as either input or output .
It does not require pull -up resistors because they are already connected internally.
Upon reset, Port 1 is configured as an input port. The following code can be used
to send alternating values of 55H and AAH to Port 1.
; Toggle all bits of continuously
MOV A,#5 5
BACK:
MOV P2,A
ACALL DELAY
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CPL A ; complement ( invert) reg. A
SJMP BACK
If Port 1 is configured to be used as an output port, then to use it as an input port
again, program it by writing 1 to all of its bits as in the following code.
; Toggle all bits of continuously
MOV A ,#0FFH ;A = FF hex
MOV P1,A ;Make P1 an input port
MOV A,P1 ;get data from P1
MOV R7,A ;save it in Reg R7
ACALL DELAY ;wait
MOV A,P1 ;get another data from P1
MOV R6,A ;save it in R6
ACALL DELAY ;wait
MOV A,P1 ;get another data from P1
MOV R5,A ;save it in R5
Port 2 (Pins 21 through 28)
Port 2 occupies 8 pins (pins 21 through 28) and can be used for both input and
output operations. Just as P1 (Port 1), P2 also does not require external Pull -up
resistors because they are already connected internally. It must be used along with
P0 to provide the 16 -bit add ress for the external memory. So it is also designated
as (A0 –A7), as shown in the pin diagram. When the 8051 is connected to an
external memory, it provides path for upper 8 -bits of 16 -bits address, and it cannot
be used as I/O. Upon reset, Port 2 is conf igured as an input port. The following
code can be used to send alternating values of 55H and AAH to port 2.
; Toggle all bits of continuously
MOV A,#55
BACK:
MOV P2,A
ACALL DELAY
CPL A ; complement (invert) reg. A
SJMP BACK
If Port 2 is configured to be used as an output port, then to use it as an input port
again, program it by writing 1 to all of its bits as in the following code.
; Get a byte from P2 and send it to P1
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MOV P2,A ;make P2 an input port
BACK:
MOV A,P2 ;get data from P2
MOV P1,A ;send it to Port 1
SJMP BACK ; keep doing that
Port 3 (Pins 10 through 17)
It is also of 8 bits and can be used as Input/Output. This port provides some extremely important signals. P3.0 and P3.1 are RxD (Receiver) and TxD (Transmitter) respectively and are collectively used for Serial Communication.
P3.2 and P3.3 pins are used f or external interrupts. P3.4 and P3.5 are used for timers
T0 and T1 respectively. P3.6 and P3.7 are Write (WR) and Read (RD) pins. These
are active low pins, means they will be active when 0 is given to them and these
are used to provide Read and Write ope rations to External ROM in 8031 -based
systems.
Dual Role of Port 0 and Port 2
xDual role of Port 0 íPort 0 is also designated as AD0 –AD7, as it can be used
for both data and address handling. While connecting an 8051 to external
memory, Port 0 can provide both address and data. The 8051 microcontrollers
then multiplexes the input as address or data in or der to save pins.
xDual role of Port 2 - Besides working as I/O, Port P2 is also used to provide
16-bit address bus for external memory along with Port 0. Port P2 is also
designated as (A8 – A15), while Port 0 provides the lower 8 -bits via A0 –A7. In
other words, we can say that when an 8051 is connected to an external memory
(ROM) which can be maximum up to 64KB and this is possible by 16-bit
address bus because we know 216 = 64KB. Port2 is used for the upper 8 -bit of
the 16 bits address, and it cannot be u sed for I/O and this is the way any
Program code of external ROM is addressed.
9.5.3 Hardware Connection of Pins
xVcc í3LQSURYLGHVVXSSO\WRWKH&KLSDQGLWLV9
xGnd í3LQSURYLGHVJURXQGIRUWKH5HIHUHQFH
xXTAL1, XTAL2 (Pin no 18 & Pin no 19) íKDVRQ -chip oscillator but
requires external clock to run it. A quartz crystal is connected between the
XTAL1 & XTAL2 pin of the chip. This crystal also needs two capacitors of
30pF for generating a signal of desired frequency. One side of ea ch capacitor
is connected to ground. 8051 IC is available in various speeds, and it all
depends on this Quartz crystal, for example, a 20 MHz microcontroller
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xRST (Pin No. 9) í,WLVDQ,QSXWSLQ and active High pin. Upon applying a
high pulse on this pin, that is 1, the microcontroller will reset and terminate
all activities. This process is known as Power -On Reset. Activating a power -
on reset will cause all values in the register to be lost. It w ill set a program
counter to all 0's. To ensure a valid input of Reset, the high pulse must be
high for a minimum of two machine cycles before it is allowed to go low,
which depends on the capacitor value and the rate at which it charges.
(Machine Cycle is the minimum amount of frequency a single instruction
requires in execution).
xEA or External Access (Pin No. 31) í,WLVDQLQSXWSLQ7KLVSLQLVDQDFWLYHlow pin; upon applying a low pulse, it is activated. In case of microcontroller
(8051/52) having on -chip ROM, the EA (bar) pin is connected to Vcc.
However, in an 8031 microcontroller that does not have an on -chip ROM, the code is stored in an external ROM and then fetched by the microcontroller. In this case, we must connect the (pin no 31) EA to Gnd to
indicate that the program code is stored externally.

xPSEN or Program store Enable (Pin No 29) - This is also an active low
pin, i.e., it is activated after applying a low pulse. It is an outpu t pin and used
along with the EA pin in 8031 based (i.e. ROMLESS) Systems to allow
storage of program code in external ROM.
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xALE or (Address Latch Enable) - This is an Output Pin and is active high.
It is especially used for 8031 IC to connect it to the external memory. It can
be used while deciding whether P0 pins will be used as Address bus or Data
bus. When ALE = 1, then the P0 pins work as Data bus and wh en ALE = 0,
then the P0 pins act as Address bus.
9.5.4 I/O Ports And Bit Addressability
It is a most widely used feature of 8051 while writing code for 8051. Sometimes
we need to access only 1 or 2 bits of the port instead of the entire 8 -bits. 8051
provides the capability to access individual bits of the ports.
While accessing a port in a single -bit manner, we use the syntax "SETB X. Y"
where X is the port number (0 to 3), and Y is a bit number (0 to 7) for data bits
D0-D7 where D0 is the LSB and D7 is the MSB. For example, "SETB P1.5" sets
high bit 5 of port 1.
The following code shows how we can toggle the bit P1.2 continuously.
AGAIN:
SETB P1.2
ACALL DELAY
CLR P1.2
ACALL DELAY
SJMP AGAIN
9.5.5 Single -Bit Instructions Instructions Function SETB bit Set the bit (bit = 1) CLR bit clear the bit (bit = 0) CPL bit complement the bit (bit = NOT bit) JB bit, target jump to target if bit = 1 (jump if bit) JNB bit, target jump to target if bit = 0 (jump if no bit) JBC bit, target jump to target if bit = 1, clear bit (jump if bit, then clear) munotes.in

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9.6 Logic Operations
9.6.1 Basics of Bitwise Operations
Now let us concentrate only on bitwise operations. We’ll learn how these bitwise
operations allows us for Setting, Inverting, Toggling, Clearing, Extracting and
Inserting bits in embedded programming. Here is a table which summarizes operations with 2 -operands. A B A | B A & B A ^ B
0 0 0 0 0
1 0 1 0 1
0 1 1 0 1
1 1 1 1 0
9.7 Data Conversion Programs
Many newer microcontrollers have a real -time clock (RTC) where the time and
date are kept even when the power is off. Very often, the RTC provides the time
and date in packed BCD. However, to display them they must be converted to
ASCII. In this section we show the application of logic and rotate instructions in
the conversion of BCD and ASCII
ASCII numbers
2Q$6&,,NH\ERDUGVZKHQWKHNH\³ƎLVDFWLYDWHG³2LOƎ+LVSURYLGHG
WRWKHFRPSXWHU6LPLODUO\+2LOLVSURYLGHGIRUWKHNH\³ƎD nd so on,
as shown in Table
ASCII Code for Digits 0 – 9

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Packed BCD to ASCII conversion
The RTC provides the time of day (hour, minute, second) and the date (year, month,
day) continuously, regardless of whether the power is on or off. However, this data
is provided in packed BCD. To convert packed BCD to ASCII, it must first be
converted to unpacked BCD. Then the unpacked BCD is tagged with Oil 0000
(30H). The following demonstrates converting from packed BCD to ASCII.
ASCII to packed BCD conversion
To convert ASCII to packed BCD, it is first converted to unpacked BCD (to get rid
of the 3), and then combined to make packed BCD. For example, 4 and 7 on the
keyboard give 34H and 37H, respectively. The goal is to produce 47H or “0100
ƎZKLFKLVSDFNHG%&'
9.8 Summary
In 8051, I/O operations are done using four ports and 40 pins. I/O in terface is
required whenever a processor drives the I/O device. The interface must have the
necessary logic to interpret the device address generated by the processor.
C language support to in line assembly gives many benefits. The C Program uses
various i nstructions elements, Pre -processor Directives, Functions, Macro &
constants, Including of the source & Header files. Basic C programming elements
are Data Types, Data Structure, Modifiers, conditional statements & Loops,
Function calls, multiple functions ; Queue & Routines. Structure is collection of all
Data types. Array of structure are helpful in configure data in Embedded
Applications. Compiler is tool for native platform Application Development.
Whereas Cross -Compiler is a tool for cross platform Application development.
Embedded C can be considered as subset of conventional C Language. Embedded
C supports almost all C instructions & incorporates a few target processor specific
functions. Embedded C also supports all Keywords, Identifiers & Data types,
Storage classes, A rithmetic & Logic operations, Array & Branching instructions.
Infinite looping is greatly used features in Embedded systems. The C function
arguments pass the variable values as well as pass reference to the functions,
Pointers, Null & Function Pointers. A data type specifies the type of data that a
variable can store such as integer, floating, character etc. When the delay subroutine is executed, the microprocessor does not execute other tasks . Logical
instructions are the instructions which perform basic logical operations such as
AND, OR, etc . The bitwise or bit -OHYHORSHUDWRUOD\¶VIRXQGDWLRQIRUELWZLVH
operations in embedded programming. 3 factors that affect accuracy of Time Delay
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9.9 Questions
Q1) Give Basics of Embedded C Program
Q2) Differentiate C & Embedded C language
Q3) Give Advantages of Embedded C
Q4) Explain Keywords used in Embedded C?
Q5) What do you mean by I/O Programming?
Q6) Write a C Program to Blink LED connected to Port 1 of 8051.
Q7) Give the Importance of Logic Operations & Their Use
Q8) Explain Data Types & Time Delay uses in 8051?
9.10 References & Future Reading
1) Book Programming in ANSI C by E Balgurusamy.
2) Book Embedded Systems Architecture, Programming & Design (Second
Edition / The McGraw Hill publications) by Raj kamal.
3) Introduction to Embedded system By Shibu K V (Tata McGraw Hill Publications)
4) Book Embedded System by Ashwini Somnathe & Abhijit Somnathe for
SYBSc IT (Sheth Publications)
5) www.google.com
6) www.youtube.com

7777777
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96Unit 4
10 DESIGNING EMBEDDED SYSTEM
WITH 8051 MICROCONTROLLER
Unit Structure
10.1 Factors to Be Considered In Selecting A Controller
10.2 Why 8051 Microcontroller:
10.3 Architecture diagram of 8051
10.4 a. The 8051 oscillator and Clock
b. Why is 11.0592 MHz crystal considered over 12 MHz?
10.5 a. External Program Memory Chip ( ROM) Interfacing
b. Data Memory interfacing
c. Interfacing External Data Memory Access
10.6 Von-Neumann Memory Model for 8051
10.7 Register Organization
a. Special Function Register ( SFR)
b. SFR Registers for the Internal Timer
10.8 Input/Output (I/ O) Ports
10.9 Chapter End Questions
10.10 Summary
10.11 Reference for further reading 
10.0 Objectives
• In this chapter one will understand what are the factors that need to be
considered while selecting a microcontroller.
• Understanding the importance of 8051 microcontroller
• Understanding how to design 8051
10.1 Factors To Be Considered In Selecting A Controller:
1. Speed of Operation :
• It is one of the most important factor that needs to be considered while
selecting microcontroller .
• The number of clocks required per instruction cycle and maximum
operating clock frequency supported by processor greatly affects the
speed of operation o f the controller.
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2. Code Memory Space:
• The target processor/controller application is written in C or any other
high level language.
• Does the controller support sufficient code memory space to hold the
compiled hex code?
3. Data Memory Space:
• Does the controller support sufficient internal data memory(ON chip
RAM) to hold run time variables and data structures?
4. Development Support
• In this it is essential to check that the controller manufacture provides
cost effective development tools.
• It also needs to be checked that manufacturer provide sample product for prototyping and sample development stuffs to alleviate the development pains.
• Does the controller support third party development tools?
• Does the manufacturer provide technical support if necessary?
5. Availability:
• This is another important factor that should be considered for selecting
the process.
• Since the product is entirely dependent on the controller, t he product
development time and time to market the product solely depends on its
availability.
• Technically it is referred as Lead Time.
• Lead time is the time elapsed between the purchase order approval and
the supply of the product.
6. Power Consumptio n:
• Power consumption of the controller should be minimum.
• It is critical factor since high power requirement leads to bulky power
supply design.
• The high power dissipation also demands for cooling fans and it will
make the overall system messy and ex pensive.
• Controller should support idle and power down modes of operation to
reduce power consumption.
7. Cost:
• It is the biggest deciding factor in selecting a controller.
• The cost should be within the reachable limit of the end user and the
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10.2 Why 8051 Microcontroller:
• It is very versatile microcontroller featuring powerful Boolean processor which supports bit manipulation instruction for Real time industrial control applications.
• 8051 supports 6 int errupts ( 2 external interrupts , 2 timer interrupts and 2 serial
interrupts), two 16 bit timers/counters, 32 I/O lines and programmable full
duplex serial interface.
• The interrupts of 8051 has two priority levels and each interrupt is allocated
fixed 8 by tes of code memory, this approach is very efficient in real time
application.
• Apart from Intel which is the original manufacturer of 8051 it is also available
through more than 20 vendors with more than 100 variants of 8051.
• It supports CAN, USB, SPI and T CP/IP interfaces, it also has integrated
ADC/DAC
• Apart from all the above features the most striking feature is its cost, which is
very low.
10.3 Architecture diagram of 8051:

Figure 10.1 Architecture of 8051 Microcontroller Functional Description of Each
Block
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• Accumulator: (Acc) Acc is an 8 bit special function register. It acts an operand register. Result is temporarily stored in this register. It is used in parallel I/O transfer.
• B Register : B register is 8 bit SFR. It is used during multiply and divide
operations. For other ope rations , it can be used as a scratchpad register.
• Program Status Word (PSW) : PSW register is 8 bit SFR. It contains program
status information. It is also used to select any one of the required register
bank.
• Stack Pointer ( SP): It is 8 bit register. It is used to point the stack memory.
The stack may reside in anywhere in on -chip memory. It is incremented
before data is stored during PUSH & CALL instructions. After reset SP is
initialized to 07h. This causes the stack begin at location 08h.
• Data Pointer (DPTR) : It is 16 bit register. It may be manipulated as a 16 bit
register or as two independent 8 bit registers. Its function is to hold a 16 bit
address. This register is used for external reference.
• Port 0 to Port 3 : Each port contains separate addres s. Using this address,
User can communicate with these ports. Each port contains latch,output
driver & input buffer.
• Serial Data Buffer : Serial data buffer contains two independent registers of
a transmit buffer register and a receiver buffer register.
R Transmit buffer is a parallel in and Serial out register.
R Receiver buffer is a Serial in and parallel out register.
R When data is moved to SBUF, it goes to transmit buffer .
R When data is moved from SBUF, it comes from the receive buffer.
• Timer Registers : Register pairs (TH0,TL0) & (TH1,TL1) are the two 16 bit
counting registers for Timer/Counter 0 and 1 respectively.
• Control Registers : The special function registers IP,IE , TMOD, TCON
SCON and PCON contain control and status information for interrupts,
timer/counters and serial port.
• Timing & Control Unit : This unit derives an necessary timing and control
signals required for the internal operations of the circuit. It derives control
signals required for controlling the external system bus. The interrupt, serial
port and timer circuits are controlled by the control signals generated by
timing & control unit.
• Oscillator : This circuit generates the basic timing clock signal for the
operation of the circuit using crystal oscillator.
• Instruction Register : Th is register decodes the opcode of an instruction to be
executed and gives information to the timing & control unit, and to generate
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• EPROM & Program Address Register : These blocks provide an onchip
EPROM and a Mechanism to internally address it.
• RAM & RAM address register : These blocks provide an onchip RAM and a
mechanism to internally address it.
• ALU : The Arithmetic And Logic Unit performs 8 bit arithmetic and logical
operations over the operands h eld by the temporary registers TMP 1 and TMP
2. User cannot access these temporary registers.
• SFR Register Banks : It is a set of registers, which can be addressed using
their respective addresses which lie in the range 80h to FFh.
10.4a. The 8051 oscill ator and Clock :

Figure 10.2:Oscillator and Clock Signal
• 8051 chips are designed to run at specific minimum and maximum frequencies. (Typically 1 MHz to 16 MHz).
• Minimum frequency implies that some internal memories are dynamic and
must always operate above a minimum frequency or data will be lost.
• Clock frequency is the smallest interval of time within the microcontroller
called the pulse, P, time.
• State is the basic time for discrete operations of a microcontroller such as
opcode fetching, opc ode decoding, opcode execution, or writing a data byte.
Two oscillator pulses form each state.
• Machine cycle is the smallest interval of time required to execute a simple
instruction, or part of a complex instruction. The machine cycle is made up
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of 6 stat es or 12 clock pulses. Program instructions may require one, two or
four machine cycles.
• Therefore the formula to calculate time taken for each instruction is given by
:
ࢀ࢚࢙࢔࢏ൌࢎࢉࢇࡹ࢔࢏ࢋࢉ࢟ࢉ࢒ࢋכ૚૛
ࢉ࢟࢘ࢇ࢚࢙࢒ࢌࢋ࢛࢘ࢗ࢟ࢉ࢔ࢋ
e.g. ADD A ,R1 : 1 Machine Cycle,. Consider Crystal frequency: 12 MHz
ࢀ࢚࢙࢔࢏ൌ૚כ૚૛
૚૛ࢠࡴࡹൌ૚ࣆࢉࢋ࢙
10.4.b. Why is 11.0592 MHz crystal considered over 12 MHz ?
• For serial communication in 8051, it is required that the internal counters
must divide the ba sic clock rate to achieve standard communication bits per
second (baud) rates.
• The standard baud rates are 19200, 9600, 4800, 2400, 1200, and 300 Hz.
• If the basic clock frequency is not divisible without a remainder, then the
resulting communication freque ncy is not standard.
• e.g. if crystal frequency is 11.0592 MHz then;
• ࢀ࢚࢙࢔࢏ൌ૚כ૚૛
૚૚Ǥ૙૞ૢ૛ࢠࡴࡹൌ૚Ǥ૙ૡ૞ࢉࢋ࢙ࣆൌૢ૛૚ǡ૟૙૙ࢠࡴ
• It is noted that 921,600Hz can be divided evenly by standard communication
baud rates, Hence 11.0592 MHz crystal is considered.
10.5 Memory Organisation:

Figure 10.3:Memory Organisation
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• 8051architecture provide lowest 4K bytes of program memory as On -Chip
memory.
• Switching between internal program memory and external program memory
is accomplished by changing the logic level of the pin External Access
(EA\----read as EA bar). EA \ pin is an active low pin.
• Connect EA \ pin to logic 1(Vcc) connects the chip to execute instruction from
program memory upto 4K (program memory location upto 0F FFFH) from
internal memory and 4K(program memory location 1000H)onwards from
external memory, while connecting EA \ pin o logic 0(GND) configures chip
to external program execution mode, where then entire code memory is
executed from the external memory.
• The control signal for external program memory execution is PSEN \(Program Strobe Enable ----PSEN \ is read as PSEN bar)
• For internal program memory fetches PSEN \ is not activated.
10.5.a External Program Memory Chip(ROM) interfacing:
• If the program memory is e xternal , 16 I/O lines are used for accessing the
external memory.
• Port 0 and Port 2 are used for external memory accessing, where initially Port
0 send lower order address when ALE signal of 8051 is high and then it
function as input port for data transfe r from the corresponding memory
location while Port 2 sends higher order address.

Figure 10.4:External Program Memory Organisation


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10.5.b Data Memory interfacing:
• The basic 8051 architecture supports 128 bytes of internal data memory and
128 bytes of Special Function Register(SFR)
• The address range for internal user data memory is 00H to 7FH while SFR
are residing at memory area 80H to FFH.
• 8051 supports interface for 64Kbytes of external data memory.
• The control signals used for external data memory accessed is Data Pointer(DPTR).
• The internal(ON chip) and external(OFF chip) data memory model of 8051
is given below

Figure 10.5: Data Memory Interfacing
10.5.c Interfacing External Data Memory access:
• External data memory address can be either one or tw o bytes long.
• Port 0 send lower order address when ALE signal of 8051 is high and if the
memory address is two bytes and if it ranges upto 64K, the entire bits of Port
2 is used for holding the higher order value of the data memory address.
• If the memory a ddress is 32K only 7 bits of Port 2 is required for addressing
the memory.
• For 16K, only 6 lines of Port 2 are required for interfacing and so on.
• The diagram below show interfacing external data memory access
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Figure 10.6: External Data Memory Interfacin g
10.5.d Internal Memory:
• The 8051’s on -chip memory consists of 256 memory bytes organized as
follows: First 128 bytes 00H to 1FH Register Banks 20H to 2FH Bit Addressable RAM 30H to 7FH General Purpose RAM Next 128 bytes 80H to FF H Special Function Registers
Below figure represents internal memory organisation
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Figure 10.7: Internal Memory Organization
10.6 Von-Neumann Memory Model for 8051:
• The code memory and data memory of 8051 can be combined together to get
benefits of Von -Neumann m odel.
• A single memory chip with read/write option can be used for this purpose.
• The program memory can be allocated to the lower memory space starting
from 0000H and data memory cane be assigned to some other specific area
after the code memory.
• For program memory fetching and data memory read operations combine the
PSEN \ and RD \ signals using AND gate and connect it to the Output
enable(OE \) signal of the memory chip.
• The diagram below shows Von Neumann Memory Model

Figure 10.8: Von -Neumann model
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Drawback:
• Accidental corruption of program memory
• Reduction in total memory space. In separate program and data memory
model the total available memory is 128KB(64KB program memory + 64KB
data memory) whereas in combine only 64KB memory is available
10.7 Register Organisation:
10.7.a Special Function Register(SFR):
• The SFR registers are located within the Internal Memory in the address range
80h to FFh. Not all locations within this range are defined.
• Each SFR has a very specific function. Each SFR has an address (within the
range 80h to FFh) and a name which reflects the purpose of the SFR.
• Although 128 byes of the SFR address space is defined only 21 SFR registers
are defined in the standard 8051.
• Undefined SFR addresses should not be accessed as this might lead to some
unpredictable results. Note some of the SFR registers are bit addressable. SFRs
are accessed just like normal Internal RAM locations.
• PSW Program Status Word ( flag register):

Figure 10.9: PSW
• Carry Flag(CY):
• This is a conventional car ry, or borrow, flag used in arithmetic operations.
The carry flag is also used as the ‘Boolean accumulator’ for Boolean
instruction operating at the bit level. This flag is sometimes referenced as the
CY flag.
• Auxiliary Flag(AC):
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• This is a conventional auxiliary carry (half carry) for use in BCD arithmetic.
• Flag 0.(F0):
• This is a general -purpose flag for user programming.
• Overflow(OV):
• This is a conventional overflow bit for signed arithmetic to determine if the
result of a signed arithmetic operation is out of range.
• Even Parity flag(P):
• The parity flag is the accumulator parity flag, set to a value, 1 or 0, such that
the number of ‘1’ bits in the accumulator plus the parity bit add up to an even
number.
• Register bank select 0 and register b ank select 1. RS0 and RS1:
These bits define the active register bank (bank 0 is the default register bank).

Figure 10.10: Register Bank
• Stack Pointer :
• The Stack Pointer, SP, is an 8 -bit SFR register at address 81h. The small
address field (8 bits) and the limited space available in the Internal RAM
confines the stack size, and this is sometimes a limitation for 8051 programmers.
• The SP contains the addr ess of the data byte currently on the top of the stack.
The SP pointer is initialised to a defined address.
• A new data item is ‘pushed’ on to the stack using a PUSH instruction which
will cause the data item to be written to address SP + 1.
• Typical instr uctions, which cause modification to the stack are: PUSH, POP,
LCALL, RET, RETI etc.
• The SP SFR, on start -up, is initialised to 07h so this means the stack will start
at 08h and expand upwards in Internal RAM.
• If register banks 1 to 3 are to be used the S P SFR should be initialised to start
higher up in Internal RAM.
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• The following instruction is often used to initialise the stack:
• MOV SP, #2Fh
• Data pointer
• The Data Pointer, DPTR, is a special 16 -bit register used to address the
external code or external data memory.
• Since the SFR registers are just 8 -bits wide the DPTR is stored in two SFR
registers, where DPL (82h) holds the low byte of the DPTR and DPH (8 3h)
holds the high byte of the DPTR.
• For example, if you wanted to write the value 46h to external data memory
location 2500h, you might use the following instructions:
• MOV A, #46h ; Move immediate 8 bit data 46h to A (accumulator) MOV
DPTR, #2504h ; Move immediate 16 bit address value 2504h to A.
• ; Now DPL holds 04h and DPH holds25h.
• MOVX @DPTR, A ; Move the value in A to external RAM location
2500h. uses indirect addressing.
• Note the MOVX (Move X) instruction is used to access external memory.
10.7.b SFR Registers for the Internal Timer:
• TCON :
• The Timer Control register is an SFR at address 88h, which is bit -
addressable. TCON is used to configure and monitor the 8051 timers.
• The TCON SFR also contains some interrupt control bits, described later.
• TMOD:
The Timer Mode register is an SFR at address 89h and is used to define
the operational modes for the timers.
TL0 (Timer 0 Low) and TH0 (Timer 0 High) are two SFR registers addressed at 8Ah and 8Bh respectively. The two registers are associated with Tim er 0.
TL1 (Timer 1 Low) and TH1 (Timer 1 High) are two SFR registers
addressed at 8Ch and 8Dh respectively. These two registers are
associated with Timer 1.
• Power Control Register
PCON (Power Control) register is an SFR at address 87h. It contains
various control bits including a control bit, which allows the 8051 to
go to ‘sleep’ so as to save power when not in immediate use.
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SCON (Serial Control) is an SFR register located at addresses 98h,
and it is bit addressable . SCON confi gures the behaviour of the on -
chip serial port, setting up parameters such as the baud rate of the
serial port, activating send and/or receive data, and setting up some
specific control flags.
SBUF (Serial Buffer) is an SFR register located at address 99 h. SBUF
is just a
• single byte deep buffer used for sending and receiving data via the on -chip
serial port.
• Interrupt Registers :
IE (Interrupt Enable) is an SFR register at addresses A8h and is used
to enable and disable specific interrupts. The MSB bit (bit 7) is used
to disable all interrupts.
IP (Interrupt Priority) is an SFR register at addresses B8h and it is bit
addressable. The IP register specifies the relative priority (high or low
priority) of each interrupt. On the 8051, an interrupt may eit her be of
low (0) priority or high (1) priority.
10.8 Input/Output (I/O)Ports:
• Port 0(P0):


Figure 10.11: I/O Port P0 Structure
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• Port-0 can be configured as a normal bidirectional I/O port or it can be used for
address/data interfacing for accessing external memory.
• When control is '1', the port is used for address/data interfacing.
• When the control is '0', the port can be used as a normal bidirectional I/O port.
• Port 1(P1):


Figure 10.12: I/O Port P1 Structure
• Port-1 does not have any alternate function i.e. it is dedicated solely for I/O
interfacing. When used as output port, the pin is pulled up or down through
internal pull -up.
• To use port -1 as input port, '1' has to be written to the latch. In this input mode
when '1' is written to the pin by the external device then it read fine. But when
'0' is written to the pin by the external device then the external source must sink
current due to internal pull -up.
• If the external device is not able to sink the current the pin voltage may rise,
leading to a possible wrong reading.
• Port 2(P2):
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Figure 10.13: I/O Port P2 Structure
• Port-2 is used for higher external address byte or a normal input/output port.
The I/O operation is similar to Port -1.
• Port-2 latch remains stable when Port -2 pin are used for external memory
access.
• Here again due to internal pull -up there is limited current driving capability.
• Port 3(P3) :
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Figure 10.14: I/O Port P3 Structure
• Each pin of Port -3 can be individually programmed for I/O operation or for
alternate function.
• The alternate function can be activated only if the corresponding latch has
been written to '1'.
• To use the port as input port, '1' s hould be written to the latch.
• This port also has internal pull -up and limited current driving capability.
10.9 Chapter End Questions
Answer the following questions
• Explain the function of PORT 0 and PORT 3
• Explain TMOD and TCON
• Explain data memory interfacing.
• List and explain factors that need to be consider while selecting microcontroller.
• Explain memory organization in details.
• Explain interfacing external data memory access
10.10 Summary:
• All the factors that needs to be considered while select ing micro -controller is
discussed.
• Various memory interfacing technique that is used to connect with micro -
controller.
• Importance and functionality of 8051 ports.
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10.11 Reference for further reading
• Embedded Systems by Rajkamal
• Introduction to embedded sys tems by Shibu K V
• https://www.tutorialspoint.com/microprocessor/microcontrollers_8051_arch
itecture.htm
• https://www.watelectronics.com/8051 -microcontroller -architecture/

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114Unit 4
11 PROGRAMMING EMBEDDED SYSTEM
Unit Structure
11.1 Structure of Embedded Program
11.2 Infinite Loop
11.3 Embedded Software Development Process
11.4 Compiling
11.5 Linking
11.6 Locating
11.7 Debugging
11.7.1 Hardware Debugging
11.7.2 Software Debugging
11.8 Chapter End Question
11.9 Summary
11.10 Reference for further reading
11.0 Objectives
From this chapter student will be able to explain the structure of embedded
program
• Students will gain the knowledge about Infinite loop usage in embedded
system
• Student will be able to gain knowledge about various debugging technique.
11.1 Structure of Embedded Program:
1. Comments:
• Comments are readable text are written to help us (the reader)
understand the code easily. They are ignor ed by the compiler and do
not take up any memory in the final code (after compilation).
• There are two ways you can write comments: one is the single line
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2. Preprocessor Directive:
• A Preprocessor Directive in Embedded C is an indication to the
compiler that it must look in to this file for symbols that are not
defined in the program.
• In C Programming Language (also in Embedded C), Preprocessor
Directives are u sually represented using #include… or #define….
• In Embedded C Programming, we usually use the preprocessor
directive to indicate a header file specific to the microcontroller,
which contains all the SFRs and the bits in those SFRs.
• In case of 8051, Keil Co mpiler has the file “reg51.h”, which must be
written at the beginning of every Embedded C Program.
3. Global Variables:
• Global Variables, as the name suggests, are Global to the program i.e.
they can be accessed anywhere in the program.
4. Local Variable s:
• Local Variables, in contrast to Global Variables, are confined to their
respective function.
5. Main Function:
• Every C or Embedded C Program has one main function, from where
the execution of t he program begins.
Example:
#include // Preprocessor Directive
void delay (int); // Delay Function Declaration
void main(void) // Main Function
{
P1 = 0x00; /* Making PORT1 pins LOW. All the LEDs are OFF.
(P1 is PORT1, as defined in reg51.h) */
while(1) // infinite loop
{
P1 = 0xFF; // Making PORT1 Pins HIGH i.e. LEDs are ON.
delay(1000);
/* Calling Delay function with Function parameter as 1000.
This will cause a delay of 1000mS i.e. 1 second */
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}
}
void d elay (int d) // Delay Function Definition
{
unsigned int i=0; // Local Variable. Accessible only in this function.

/* This following step is responsible for causing delay of 1000mS (or as per the
value entered while calling the delay function) */
for(;d> 0;d–)
{
for(i=250;i>0;i – -);
for(i=248;i>0;i – -);
}
}
11.2 Infinite Loop
• Almost every embedded ap -plication involves delay programming.
Embedded applications employ delay programming for waiting for a
fixed time interval till a device is ready, for inserting delay between
displays updating to give the user sufficient time to view the contents displayed, delays involved in bit transmission and reception in asynchronous serial transmissions like I2C, I -Wire data transfer, delay
for key de -bouncing etc.
One of the most fundamental differences between programs developed
for embedded systems and those written for other computer platforms
is that the embedded programs almost always end with an infinite loop.
Some delay requirements in .embedd ed application may be critical,
meaning delay accuracy should be within a very narrow tolerance band.
Typical example is delay used in bit data transmission. If the delay
employed is not accurate, the bits may lost while transmission or
reception. Certa in delay requirements in embedded application may not
be much critical, e.g. display updating delay.
It is easy to code delays in desktop applications under DOS or Windows
operating systems. The library function delay0 in DOS and Sleep O in
Windows provi des delays in milliseconds with reasonable accuracy.
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Delay routine requires a complete re -work if the target clock frequency
is changed. Normally 'for loops' are used for coding delays. In finite
loops are created using various loop control instructions like while (),
do while (), for and goto labels.
The super loop created by while (1) instruction in a traditional super
loop based embedded firmware design is a typical example for infinit e
loop in embedded application development.
• The infinite loop is necessary because the embedded software's job is never
done. It is intended to be run until either the world comes to an end or the
board is reset, whichever happens first.
• In addition, most embedded systems have only one piece of software
running on them. And although the hardware is important, it is not a digital
watch or a cellular phone or a microwave oven without that embedded
software. If the software stops running, the hardware is rende red useless.
• So the functional parts of an embedded program are almost always surrounded by an infinite loop that ensures that they will run forever.
Infinite loop using while:
While(1)
{
}
Infinite loop using do while:
do
{
} while(1);
Infinite loop using for :
for ( ; ; ; )
{
}
Infinite loop using goto (‘goto' when combined with a 'label' can create
infinite loops)
label : // Task to be repeated
//………..
//………...
Goto label ;

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11.3 Embedded Software Development Process

• The process of converting the source code representation of your embedded
software into an executable binary image involves three distinct steps.
• First, each of the source files must be compiled or assembled into an object
file.
• Second, all of the object files that result from the first step must be linked
together to produce a single object file, called the relocatable program.
• Finally, physical memory addresses must be assigned to the relative offsets
within the relocatable program in a process called relocation.
• The result of this third step is a file that contains an executable binary image
that is ready to be run on the embedded system.
• The diagram above shows the embedded development process.
11.4 Compiling
• The job of a compiler is mainly to transla te programs written in some
human -readable language into an equivalent set of opcodes for a particular
processor.
• In that sense, an assembler is also a compiler (you might call it an "assembly
language compiler") but one that performs a much simpler one -to-one
translation from one line of human -readable mnemonics to the equivalent
opcode.
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• Together these tools make up the first step of the embedded software build
process.
• Each processor has its own unique machine language, so you need to choose
a compiler t hat is capable of producing programs for your specific target
processor.
• In the embedded systems case, this compiler almost always runs on the host
computer. It simply doesn't make sense to execute the compiler on the
embedded system itself.
• A compiler su ch as this -that runs on one computer platform and produces
code for another -is called a cross -compiler.
• The use of a cross -compiler is one of the defining features of embedded
software development.
• The GNU C/C++ compiler ( gcc ) and assembler (as ) can be configured as
either native compilers or cross -compilers. As cross -compilers these tools
support an impressive set of host -target combinations.
• Regardless of the input language (C/C++, assembly, or any other), the
output of the cross -compiler will be an o bject file. This is a specially
formatted binary file that contains the set of instructions and data resulting
from the language translation process.
The contents of an object file can be thought of as a very large,
flexible data structure. The structure of the file is often defined by a
standard format such as the Common Object File Format (COFF) or
Executable and Linkable Format (ELF).
If you’ll be using more than one compiler (i.e., you’ll be writing parts
of your program in different source languag es), you need to make sure
that each compiler is capable of producing object files in the same
format; gcc supports both of the file formats previously mentioned.
Although many compilers (particularly those that run on Unix
platforms) support standard ob ject file formats such as COFF and
ELF, some others produce object files only in proprietary formats. If
you’re using one of the compilers in the latter group, you might find
that you need to get all of your other development tools from the same
vendor.
Most object files begin with a header that describes the sections that
follow. Each of these sections contains one or more blocks of code or
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However, the compiler has regrouped these blocks into related
sections. For example, in gcc all of the code blocks are collected into
a section called text, initialized global variables (and their initial
values) into a section called data, and uninitialized global variables
into a section called bss.
11.5 Linking
• All of the object files resulting from step one must be combined in a special
way before the program can be executed.

• The object files themselves are individually incomplete, most notably in that
some of the internal variable and function refer ences have not yet been
resolved.
• The job of the linker is to combine these object files and, in the process, to
resolve all of the unresolved symbols.
• The output of the linker is a new object file that contains all of the code and
data from the input object files and is in the same object file format. It does
this by merging the text, data, and bss sections of the input files.
• So, when the linker is finished executing, all of the machine language code
from all of the input object files will be i n the text section of the new file, and
all of the initialized and uninitialized variables will reside in the new data
and bss sections, respectively.
• While the linker is in the process of merging the section contents, it is also
on the lookout for unresolved symbols.
For example, if one object file contains an unresolved reference to a variable named foo and a variable with that same name is declared in
one of the other object files, the linker will match them up.
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The unresolved reference will be replaced with a reference to the actual
variable. section, its entry in the symbol table will now contain that address.
The GNU linker (ld) runs on all of the same host platforms as the GNU
compiler. It is a command -line tool that takes the names of all the object
files, and possibly libraries, to be linked as arguments.
With embedded software, a special object file that contains the compiled startup code, which is covered later in this section, must also
be included within this list.
The GNU linker also has a scripting language that can be used to
exercise tighter control over the object file that is output.
If the same symbol is declared in more than one object file, the linker
is unable to proceed. It will likely complain to the programme r (by
displaying an error message) and exit.
On the other hand, if a symbol reference remains unresolved after all
of the object files have been merged, the linker will try to resolve the
reference on its own.
The reference might be to a function, suc h as memcpy, strlen, or
malloc, that is part of the standard C library, so the linker will open
each of the libraries described to it on the command line (in the order
provided) and examine their symbol tables.
If the linker thus discovers a function or variable with that name, the
reference will be resolved by including the associated code and data
sections within the output object file. Note that the GNU linker uses
selective linking, which keeps other unreferenced functions out of the
linke r’s output image.
After merging all of the code and data sections and resolving all of the
symbol references, the linker produces an object file that is a special
“relocatable” copy of the program.
In other words, the program is complete except for on e thing: no
memory addresses have yet been assigned to the code and data sections
within. If you weren’t working on an embedded system, you’d be
finished building your software now.
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Even if your embedded system includes an operating system, you’ll
probably still need an absolutely located binary image.
In fact, if there is an operating system, the co de and data of which it
consists are most likely within the relocatable program too. The entire
embedded application —including the operating system —is frequently
statically linked together and executed as a single binary image.
Compile and Linking Proces s can be well explained by below flowchart

11.6 Locating:
• The tool that performs the conversion from relocatable program to
executable binary image is called a locator.
• It takes responsibility for the easiest step of the three. In fact, you will hav e
to do most of the work in this step yourself, by providing information about
the memory on the target board as input to the locator.
• The locator will use this information to assign physical memory addresses
to each of the code and data sections within the relocatable program.
• It will then produce an output file that contains a binary memory image that
can be loaded into the target ROM.
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• In many cases, the locator is a separate development tool. However, in the
case of the GNU tools, this functional ity is built right into the linker.
11.7 Debugging:
• Debugging in embedded applications is the process of checking the firmware
execution, monitoring the target processor, register and memory while the
execution process is going ON.
• Debugging in embedded application is broadly classified into two types:
i. Hardware debugging
ii. Software debugging
11.7.1 Hardware debugging
• Even though the firmware is bug free and everything is intact in the board,
your embedded product need not function as per the expected behaviour in
the first attempt for various hardware related reasons like dry soldering of
components, missing connections in the due to any un -noticed errors in the
PCB layout design, misplaced components, si gnal corruption due to noise,
etc.
The only way to sbrt out these issues and figure out the real problem
creator is debugging the target board. Hardware debugging is not
similar to firmware debugging.
Hardware debugging involves the monitoring of va rious signals
The various hardware debugging tools are as follows:
i. Magnifying glass or lens:

You might have noticed watch repairer wearing a small magnifying
glass while engaged·in repairing a watch. They use the magnifying
glass to view the m inute components inside the watch in an enlarged
manner so that they can easily work with them.
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Similar to a watch repairer, magnifying glass is the pri -mary hardware
debugging tool for an embedded hardware debugging professional.
A magnifying glass is a powerful visual inspection tool. With a
magnifying glass (lens), the surface of the target board can be examined
thoroughly for dry soldering of components, missing components,
improper placement of components, improper.soldering, track (PCB
connectio n) damage, short of tracks, etc.
Nowadays high quality magnifying stations are available for visual
inspection. The magnifying station incorporates magnifying glasses
attached to a stand with CFL tubes for providing proper illumination
for inspection. T he station usually incorporates multiple magnifying
lenses. The main lens acts as a visual inspection tool for the entire
hardware board whereas the other small lens within the station is used
for magnifying a relatively small area of the board which requi res
thorough inspection.
ii. Multimeter:

I believe the name of the instrument itself is sufficient to give· an
outline of its usage. A multimeter is used for measuring various
electrical quantities like voltage (Both AC and DC), current (DC as
well as AC), resistance, capacitance, continuity checking, transistor
checking, cathode and anode identification -of diode, etc.
Any multimeter will work over a specific range for each measurement.
A multimeter is the most valuable tool in the toolkit of an -embedded
hardware developer.
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It is the primary debugging tool for physical contact based hardware
debugging and almost all developers start debugging the hardware
with it.
In embedded hardware debugging it is mainly used for checking the
circuit continuity between different points on the board, measuring
the supply voltage, checking the signal value, polarity, etc.
Both analog and digital version s of a multimeter are available. The
digital version is preferred over analog the one for various reasons
like readability, accuracy, etc. Fluke, Rishab, Philips,. etc. are the manufacturers of commonly available high quality digital multimeters
iii. CRO:

Cathode Ray Oscilloscope (CRO) is a little more sophisticated tool
compared to a multimeter. You might have studied the operation and
use of a CRO in your basic electronic lab.
Just to refresh your brain, CRO is used for waveform capturing and
analysis, measurement of signal strength, etc.
By connecting the point under observation on the target board ts>, the
Channels of the Oscilloscope, the waveforms can be captured and
analysed for expected behaviour.
CRO is a very good tool in analysing in terference noise in the power
supply line and other signal lines.
Monitoring the crystal oscillator signal from the target board is a typical
example of the usage of CRO for waveform capturing and analysis in
target board debugging. CROs are available i n both analog and digital
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versions. Though Digital CROs are costly, feature wise they are best
suited for target board debugging applications.
Digital CROs are avail -able for high frequency support and they also
incorporate modern techniques for recordi ng waveform over a period
of time, capturing waves on the basis of a configurable event (trigger)
from the target board ( e.g. High to low transition of a port pin of the
target processor).
Most of the modern digital CROs contain more than one channel a nd it
is easy to capture and analyse various signals from the target board
using multiple channels simultaneously.
Various measurements like phase, amplitude, etc. is also possible with
CROs. Tektronix, Agilent, Philips, etc. are the manufacturers of hi gh
precision good quality digital CROs.
iv. Logic analyzer:

A logic analyser is the big brother of digital CRO. Logic analyser is
used for capturing digital data (logic 1 and 0) from a digital circuitry
whereas CRO is employed in capturing all kinds of waves including
logic signals.
Another major limitation of C RO is that the total number of logic
signals/waveforms that can be ·captured with a CRO is limited to the
number of channels.
A logic analyser contains special con -nectors and clips which can be
attached to the target board for capturing digital data.
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In target board de -bugging applications, a logic analyser captures the
states of various port pins, address bus and data bus I of the target
processor/controller, etc.
Logic analysers give an exact reflection of what happens when a
particular line of firmware is running.
This is achieved by capturing the address line logic and data j line logic
of target hardware. Most modern logic analysers contain provisions for
storing captured selecting a desired region of the captured waveform,
zooming selected region of the captured waveform, etc. Tektronix,
Agilent, etc. are the giants in the logic analyser market.
v. Function generator:

Function generator is not a debugging tool. It is an input signal simulator tool.
A function generator is capable of producing various periodic waveforms
like sine wave, square wave, saw -tooth wave, etc. with different frequencies
and amplitude.
Sometimes the target board may require some kind of periodic waveform
with a particular frequency as input to some part of t he board.
Thus, in a debugging environment, the function generator serves the purpose
of generating and supplying required signals.
11.7.2 Software Debugging:
• Software debugging is concerned with the monitoring declaration of processor directives, variables associated with the program and functions.
• The various method of Software debugging are as follows
i. Incremental Debugging Techniques.
ii. Inline Break Point Based Software Debugging
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• Incremental Debugging Techniques.
In this technique the entire code is not burned into the EEPROM chip.
The entire code is divided into many modules and each module is
burned one after the other.
After burning t he first module it is check for errors by running it, if no
error is detected then other module is burned.
This technique is time consuming but it is more reliable debugging
technique.
This debugging technique is one time process once the software is
tested it can go for mass production.
This technique is widely used in small, simple system developments
and in those products where time is not a big constraint.
• Inline Break Point Based Software Debugging
It is a primitive method of software debugg ing.
In this technique we insert an inline debugging code immediately after
reaching at a specified point of the code.
The debug code is a “printf” command which prints a string as per the
software depending on the execution of the software at the inli ne debug
code.
11.8 Chapter End Questions
Answer the following questions.
1. Explain structure of embedded program with suitable example.
2. Why infinite loop is preferred in embedded system? Give example.
3. Explain Software Debugging
4. What is hardware debugging? Explain any 2 in detail.
5. What is Inline break point?
6. Explain Linker.
7. Explain locator.
8. What is compiler?

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11.9 Summary
In depth explanation of various terms associated with embedded program was
discussed and understood.
The program flow concept was understood through embedded structure
program.
In depth hardware and software debugging technique using various electronic tools such as CRO, Multimeter, Logic Analyser was discussed.
11.10 Reference for furthe r reading
Introduction to embedded systems by Shibu K V
The 8051 Microcontroller and Embedded Systems by Muhammad Ali Mazidi
DyVuw.png (1920×1080) (imgur.com)
Compiling, Linking, and Locating | Barr Group
Basics of Embedd ed C Program : Introduction, Structure and Example
(electronicshub.org)
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130Unit 5
12 REAL TIME OPERATING SYSTEM
Unit Structure
12.1 Objectives
12.2 Introduction
12.3 Overview
12.4 Operating System Basics
12.4.1 Task & Task States
12.4.2 Task Synchronization
12.4.3 Scheduler
12.4.4 Ready list
12.4.5 Context Switch
12.5 Types of Operating System
12.6 Real Time Characteristics
12.7 Selection Process of RTOS
12.8 Design and Development
12.9 Embedded System Development Environment – IDE
12.9.1 Best Embedded Software Development Tools
12.9.2 Software Development Steps
12.9.3 Life without IDEs
12.9.4 Using IDEs
12.9.5 Choosing an IDE
12.10 The Microcontroller Development Cycle
12.11 Types of File Generated on cross compilation
12.12 Disassembler / De-Compiler
12.13 Simulators & Emulator
12.14 Debugger
12.15 Embedded Product Development Life -Cycle
12.16 Trends in Embedded Industry
12.17 Summary
12.18 Questions
12.19 References & Future Reading
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12.1 Objectives
xTo learn about the characteristics of Real time Operating system (RTOS) .
xTo have a knowledge about embedded operating system & its building
blocks .
xTo understand the kernel services of an operating system.
xTo learn about Operating system basics & selection of RTOS.
xTo Design & Develops RTOS .
xTo study Embedded IDE .
xTo understand the concept of Embedded Development Life cycle (EDLC).
12.2 Intro duction
We know that a n embedded operating system is a small -scale computer system with a limited number of features. It is designed to carry out a function or a
set of functions of an electronic product . Embedded operating system is also known
as Real time operating system (RTOS). In the most embedded OSs, the application
are built in to the OS or part of the OS, so they are loaded immediately when the
OS starts.
For instance, all mobile phones have an integrated embedded operating s ystem
software like Android or I OS that starts up when the phone is switched on. Many
modern electronic devices are based on Arduino or Raspberry PI . Raspberry PI
devices often run an ARM -based Linux kernel , but there are actually a number of
different operating systems that can be run on Raspberry PI devices.
In contrast to an operating system for a general -purpose computer , an embedded
operating system can be quit e limited in terms of function depending on the device
in question; the system may only run a single applicati on. Modern systems require
better functionality, more options and opportunities. That is why the popularity of
real-time operating systems is rapidly growing in the world of embedded solutions.
Guaranteeing the timely execution of high -priority tasks is e xtremely important for
critical or lifesaving applications and real -time systems that have strict deadlines.
One of the most obvious reasons is multitasking. This is unnecessary with a simple
system that only has a couple of tasks running in sequence. However, if you need
to perform many tasks simultaneously, RTOS is at your service. It allows the
developer to ru n a number of tasks concurrently. In case your embedded system
has strict task prioritization, the pre -emptive scheduler of an RTOS makes it
possible to switch to a high -priority operation at any time, ensuring that it will be
completed first. A developer has no need to control the task execution because an
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12.3 Overview
A real -time operating system (RTOS) is an operating system (OS) intended to serve
real-time applications that process data as it comes in, typically without buffer
delays. Processing time requirements (including any OS delay) are measured in
tenths of seconds or shorter increments of time. I n a RTOS, Processing time
requirement are calculated in tenths of second’s increments of time. Time -bound
system can be defined a s fixed time constraints. In this type of system, processing
must be done inside the specified constraints. Otherwise, the system will fail.
Real-time operating systems (RTOSs) are often used to develop applications for
systems with complex time and resour ce con straints. This situation often specifies laboratory automation where one or more computers must synchronize the activities among one or more instruments involving time, process, or precedent
constraints. RTOSs are deterministic by design, which allows them to meet
deadlines associated with external events using a limited set of resources. Advances
in modern development tools and frameworks have made RTOSs more accessible
to developers of all levels.
Devel oping applications for RTOSs used to be a job for the most skillful developers
not only due to the complexity of the application, but also due to the need to use
in-circuit emulators or very sophisticated cross -development platform s. Advances
in tools, lan guages and frameworks, however, have made the development of
applications for real -time systems easier. In the next sections, we examine certain
important aspects of RTOSs. Our intent is to provide information to allow you to
understand the concepts in thi s area, to help you determine when a RTOS will
benefit an application and to stimulate your interest to learn more.
12.4 Operating System Basics -
The Operating system is a software in be tween hardware device and user. Operating
system is a platform from where user can easily get communication with hardware
device. Operating system manages the all Input/output services.

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OS supports the all extended devices. Operating system is a combination of
resources manager and peripheral device. The kernel is a core system in operating
system. It is responsible for managing the interaction in between user application
and device driver like CPU, Memory and Devic e etc. Kernel handle the
peripherals devices all input/output requested. Kernel code is loaded into a
separated memory space, which is protected from user space. In a kernel space,
kernel handles all hardware devices su ch as hard disk running process task. In
control user space, handle application program like browser, audio/video player.
12.4.1 Tasks & Task states
Task is a basic piece of software that can be executed of others. In multitasking
multiple task is executed at a time, it executed parallel . Operating system is
responsible for deciding which task perform the task first . Task context record the
all informa tion about the task states, before task taking control of it. The utility
programs may also be considered tasks or subtask as all program may make
request of other program. It's easy to confuse the terms Multithreading and
multitasking. Multithreading is t he management of multiple uses of the same
program.
The terms task and process are often used interchangeably, although some operating systems make a distinction between the two. The terms task and process are often used interchangeably, although some ope rating
systems make a distinction between the two.
Task is that executing unit of computation, which is controlled by OS process
scheduling mechanism, which lets it execute on the CPU and OS process resource -
management mechanism that lets it use the system memory and other system -
resources such as network, file, display or printer .
Task states


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¾Start state
The task has been created and memory allotted to its structure O However, it
is not ready and is not schedulable by kernel.
¾Ready (Active) State
The created task is ready and is schedulable by the kernel but not running at
present as another higher priority task is scheduled to run and gets the system
resources at this instance.
¾Running state
Executing the codes and getting the system resources at this instance. It will
run till it needs some IPC (input) or wait for an event or till it gets preempted
by another higher priority task than this one.
¾Waiting state
A task is pending while it waits for an input from the keyboard or a file. The
scheduler then puts it in the blocked state
¾Terminated or Exit
Once the process finishes its execution, or it is terminated by the operating
system, it is move d to the terminated state where it waits to be removed from
main memory.
12.4.2 Task Synchronization
All the tasks in the multitasking operating systems work together to solve a larger
problem and to synchronize their activities, they occasionally communicate with
one another. For example, in the printer sharing device the printer task doesn’t have
any wo rk to do until new data is supplied to it by one of the computer tasks. So the
printer and the computer tasks must communicate with one another to coordinate
their access to common data buffers.
One way to do this is to use a data structure called a mutex . Mutexes are mechanisms provided by many operating Systems to assist with task synchronization. A mutex is a multitasking -aware binary flag. It is because the
processes of setting and clearing the binary flag are atomic (i.e. these operations
cannot be in terrupted). When this binary flag is set, the shared data buffer is
assumed to be in use by one of the tasks. All other tasks must wait until that flag is
cleared before reading or writing any of the data within that buffer. The atomicity
of the mutex set and clear operations is enforced by the operating system, which
disables interrupts before reading or modifying the state of the binary flag.
MULTIPLE TASKS WAITING:
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We now have two tasks, Task 2 and Task 3 blocked waiting on the SO. Task 1 now
reaches the synchronisation point and signals the event. Again we could have the
case of bilateral and unilateral sync, though typically Task 1 doesn’t block if no
other task is waiting (unilateral model).
12.4.3 Schedulers
This is the piece of the ope rating system that decides which of the ready tasks has
the right to use the processor at a given time. It simple checks to see if the running
task is the highest priority ready task.
• Some of the more common scheduling algorithms:
1. First -in-first-out
First-in-first-out (FIFO) scheduling describes an operating system which is
not a multitasking operating system. Each task runs until it is finished, and
only after that is the next task started on a first come first served basis.
2. Shortest job first
Shortest job first scheduling uses algorithms that will select always select a
task that will require the least amount of processor time to complete.
3. Round robin
Round robin scheduling uses algorithms that allow every task to execute for
a fixed amount to time. A running task is interrupted a put to a waiting state
if its execution time expires.
Schedulers are special system software which handle process scheduling in
various ways. Their main task is to select the jobs to be submitted into the
V\VWHPDQGWRGHFLGHZKLFKSURFHVVWRUXQ6FKHGXOHUVDUHRIWKUHHW\SHVí
xLong -Term Scheduler
xShort -Term Scheduler
xMedium -Term Scheduler
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¾Long Term Scheduler :-
It is also called a job scheduler . A long -term scheduler determines
which programs are admitted to the system for processing. It selects
processes from the queue and loads them into memory for execution.
Process loads into the memory for CPU scheduling.
The primary objective of the job scheduler is t o provide a balanced mix
of jobs, such as I/O bound and processor bound. It also controls the
degree of multiprogramming. If the degree of multiprogramming is
stable, then the average rate of process creation must be equal to the
average departure rate of processes leaving the system. On some
systems, the long -term scheduler may not be available or minimal.
Time -sharing operating systems have no long term scheduler. When a
process changes the state from new to ready, then there is use of long -
term scheduler .
¾Short Term Scheduler
It is also called as CPU scheduler . Its main objective is to increase
system performance in accordance with the chosen set of criteria. It is
the change of ready state to running state of the process. CPU scheduler
selects a proc ess among the processes that are ready to execute and
allocates CPU to one of them. Short -term schedulers, also known as
dispatchers, make the decision of which process to execute next. Short -
term schedulers are faster than long -term schedulers.
¾Medium T erm Scheduler
Medium -term scheduling is a part of swapping. It removes the processes from the memory. It reduces the degree of multiprogramming. The medium -term scheduler is in -charge of handling the swapped out -processes. A running process may become
suspended if it makes an I/O request. A suspended processes cannot
make any progress towards completion. In this condition, to remove the process from memory and make space for other processes, the suspended process is moved to the secondary storage. This pr ocess is
called swapping and the process is said to be swapped out or rolled out.
Swapping may be necessary to improve the process mix.
12.4.4 Context Switch
A context switch is the mechanism to store and restore the state or context of a CPU
in Process Control block so that a process execution can be resumed from the same
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processe s to share a single CPU. Context switching is an essential part of a
multitasking operating system features.
When the scheduler switches the CPU from executing one process to execute
another, the state from the current running process is stored into the pr ocess control
block. After this, the state for the process to run next is loaded from its own PCB
and used to set the PC, registers, etc. At that point, the second process can start
executing.

12.5 Types of Operating System
12.5.1 General Operating System
xDistributed OS
xBatch OS
xMultitasking OS
xNetwork OS
xMobile OS
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12.5.2 Real -Time OS
Real Time system complete its work & deliver its services on time. Real -Time
operating systems serve real -time systems & implies deterministic in timing
behavior. RTOS are useful where many events occur in a short time or certain
deadlines, such as real -time simulations. Functions of RTOS are Task
management, Scheduling, Resource allocation, Interrupt handling etc. Application RTOS (Deadline) Hardware Fig - Simple RTOS
The super loop concept – Task Execution model for firmware executes the
task subsequently in order which the tasks listed within the loop. Here every
task is repeated at regular interval & task execution is non real time. Because
there are no operating system to return to or an embedded device is running until
the power supply is removed. So, to run set of statements, we need a loop that
must not be finished , such kind of loops are known as 'Super Loop' or 'Infinite
Loop'.
Advantages of Real -Time OS
xIt provides more output from all the resources as there is maximum
utilization of embedded systems.
xWork done within deadlines.
xIt provides the best management of memory allocation.
xThese systems are always error -free.
xThese operating systems focus more on running applications than those
in the queue.
xShifting from one task to another takes very little time
Disadvantages of Real -Time OS
xSystem resources are extremely expensive and are not so good.
xThe algorithms used are very complex.
xOnly limited tasks can run at a single time.
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Examples of Real -Time OS: Medical imaging systems, robots, Coffee
wending machine, Flight control system, Anti Lock breaking system for
vehicles etc.
Types of the real -time operating system are:
xHard real -time OS
The hard real -time OS is the operating system for mainly the
applications in which the slightest delay is also unacceptable. The time
constraints of such applications are very strict. Such systems are built
for life -saving equipment like parachutes, airbag s, Nuclear power plant
control etc . which immediately need to be in action if an accident
happens. Flexibility not allowed & All deadlines must be followed.
xSoft real -time OS
The soft real -time OS is the operating system for applications where time
cons traint is not very strict. In a soft real -time system, an important task
is prioritized over less important tasks, and this priority remains active
until the completion of the task. Here Tasks are performed as fast as
possible (Best Affordable system). Furthermore, a time limit is always
set for a specific job, enabling short time delays for future tasks, w hich
is acceptable. For Example - Multimedia network, Online Database &
Games, virtual reality, reservation system, etc.
12.6 Real Time Characteristics:
Real-time System is a system that is put through real time which means response
is obtained within a specified timing constraint or system meets the specified
deadline. Real time system is of two types – Hard and Soft. Both are used in
different cases. Ha rd real time systems are used where even the delay of some nano
or micro seconds are not allowed. Soft real time systems provide some relaxation
in time expression.
Following are the some of the characteristics of Real -time System:
Time Constraint
Time constraints related with real -time systems simply means that time interval
allotted for the response of the ongoing program. This deadline means that the task
should be completed within this time interval. Real -time system is responsible fo r
the completion of all tasks within their time intervals.
Correctness: -
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produce correct result within the given time interval. If the result is not obtained
within the given time interval then also result is not considered correct. In real -time
systems, correctness of result is to obtain correct result in time constraint.
Embedded: -
all the real -time systems are embedded now -a-days. Embedded system means that
combination of ha rdware and software designed for a specific purpose. Real -time
systems collect the data from the environment and passes to other components of
the system for processing.
Safety :-
Safety is necessary for any system but real -time systems provide critical safety.
Real-time systems also can perform for a long time without failures. It also recovers
very soon when failure occurs in is system and it does not cause any harm to the
data and information.
Concurrency: -
Real-time systems are concurrent tha t means it can respond to a several number of
processes at a time. There are several different tasks going on within the system
and it responds accordingly to every task in short intervals. This makes the real -
time systems concurrent systems.
Distributed: -
In various real -time systems, all the components of the systems are connected in a
distributed way. The real -time systems are connected in such a way that different
components are at different geographical locations. Thus all the operations of real -
time s ystems are operated in distributed ways.
Stability: -
Even when the load is very heavy, real -time systems respond in the time constraint
i.e. real -time systems does not delay the result of tasks even when there are several
task going on a same time. This br ings the stability in real -time systems.
12.7 Selection process of RTOS
Colin Walls of mentor graphics discussed whether or not you need to use an OS
and if so, whether it will be a free, open source version . While selecting real time
operating system for an embedded system Performance is the most important factor
required to be considered while selecting for a RTOS . RTOS systems are error -
free. Therefore, there is no chance of getting an error while performing the task. A
good RTS should be capable, and it has some extra features like how it operates to
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The process of selecting an operating system for an embedded system is outlined
and reviewed. On Desktop computer the selection of an operating system is largely
a matter of taste. Having conclude that an OS is required for a project, there is the
question of making a selection. There are four option: select high end operating
system, such as Linux or an embedded variant of windows; select a real time
operating system from among many choices; deploy one of the free operating
system that are widely available.
12.8 DESIGN AND DEVELOPMENT
Design and develop tiny RTOS for low cost, vehicle monitoring system we plot
sensors on one board for monitoring vehicle so this board provide security to the
vehicle's owner. The proposed system would use new technology based on
embedded board and its advanced database at a real -time for storing all updates of
sensors. The proposed system wo rks on atmega328 microcontroller of avr family
which is used for handling vehicle tracking sensors on this board. If the speed of
vehicle crosses the limit then alert message will display on your smartphone these
all sensors worked in real time means all a re work simultaneously. Each sensor
provides a specified time delay. This operating system has to respond quickly. The
microcontroller is connected to owner's mobile via Bluetooth module. These all
sensors provide all its sensor status to the vehicle owner s on smartphone.so all the
status can be viewed by the owner to check the vehicle condition. All the previous
history of sensors stored in the database.
12.9 Embedded System Development Environment – IDE
12.9.1 Introduction of IDE
An Integrated Development Environment (IDE) is a software application that
provides a programming environment to streamline developing and debugging
software. Rather than performing all the steps required to make an executable
program as unrelated individual tasks, it brings all the tools needed into one
application and workspace. Each of the tools has an awareness of the environment,
and they work together to present a seamless development set for the developer.
Even a simple search for IDEs will turn up quite a few c hoices. IDEs are
available from Open Source communities, vendors, and software companies. They
range from free to pricing dependent upon the number of licenses required. There
isn't a standard for IDEs and each has its own capabilities, along with streng ths and
weaknesses. Generally, an IDE provides an easy -to-use interface, automates
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screen. It can also provide the link from a development operating system to an
application target platform, like a desktop environment, smartphone or microprocessor.
12.9.2 Best Embedded Software Development Tools
Here’s the list of the best embedded software development tools
12.9.2.1 NetBeans
NetBeans is a free embedded software development tool that allows you to create
apps using the most popular programming languages. This C ++ IDE has a
distribution for all popular OS, and for all other platforms, you can build NetBeans
on your own from the source.
Advantages:
xFree;
xHas cross -platform support;
xLarge selection of plugins;
xCode completion, refactoring tools;
xA welcoming community of developers.
Disadvantages:
xSlow start-up;
xProblems with your cache when building ready -made programs;
xNeeds JDK for installation.
12.9.2.2 PyCharm
Based on our team’s experience, PyCharm is the best Python embedded software
development tool with both free and paid options. PyCharm is available on all
popular OS.
This program supports out -of-the-box Python development with the ability to
directly run and debug any code. In addition, the IDE has project support and source
contr ol.
Advantages
xSupp ort for everything and everyone
xA good community
xInit feature “out of the box”.
Disadvantages :
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12.9.2.3 Microsoft Visual Studio
Visual Studio is an IDE for embedded software development that allows you to
develop both console applications and applications with a graphical interface,
including those with suppo rt for Windows Forms technology. It is also suitable for
building websites, web applications, and web services for all supported platforms.
Advantages:
xA free version; Built -in command -line interface;
xAPI for connecting additional debugging tools;
xA complete set of developer tools for creating and cloning Git repositories,
managing branches, and resolving merge conflicts right in the C ++ IDE;
xAn extensive set of add -ons to expand the basic functionality.
Disadvantages:
xHigh cost of pai d versions – Professional and Enterprise (from $ 45 per
month);
xHigh requirements for “hardware”;
xLack of any Linux versions.
12.9.2.4 CodeLite
CodeLite is a free embedded software development that runs on a variety of
operating systems. The interface is intuitive and straightforward, making it a
suitable choice for beginners. Note that the latest versions of this C ++ IDE support
PHP and Node.js projects .
Advantages:
xPowerful code completion tool based on its parser
xPlugins for working with Git and SVN & Built -in debugger.
Disadvantages: Complicated interface
12.9.3 Software Development Steps
In any environment, to develop executable software you need to create source
file(s), compile the source files to produce machine code (object files), and link the
object files with each other and any libraries or other resources required to
produce an executable file.
Source files contain the code statements to do the tasks your program is being
created for. They contain program statements specific to the language you are
using. If programming in c, the source files contain c code statements; java source
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"myfile.c". Compilers translate the source files to appropriate machine level code
for the target environment. Linkers take all the object files required for a program
and link them together, assigning memory and registers to variables, setting up
data. They also link in library files to support operating system tasks and any other
files the program needs. Linkers output executable files.
12.9.4 Life Without IDEs
When not using an IDE, developers use an editor, compiler, and linker installed on
their development machine to create code files, compile, and link them. Using the
editor to create a source file, the code blocks, comments, and program statements
are enter ed and the file saved. There are no "corrective actions," taken as the editor
doesn’t know this is supposed to be a "source file" as opposed to notes for class! If
working in a position -dependent language like Python, the developer would have
to be very careful about indenting. The file has to be saved with the correct file
extension and in a directory where the compiler can find it.
Each source file has to be compiled separately; if the program has a few source
files, they all have to be named separatel y in the compiler. When invoking the
compiler, it has to be directed to look in the correct directory for the source
files and where the output files should be stored. If there is an error in the source
file, the compiler will output messages and fail to complete. For any errors, the
developer goes back and edits the source file, working from line numbers and
compiler messages to fix the problems... and these steps continue until all the
source files compile without errors.
When linking, each object file is specified as being part of the build. Again, the
locations for the object files and executable are given. There may be errors at this
point because it isn’t until the entire program is linked that some errors can be
detected. Assuming the linker finds all the variables and functions, it produces a
file that can be run. If the program is run and it works, all's well! If it seems to do
nothing.... that means it's debugging time! Since there is no insight to what the
program is doing, the developer ma y go back and put in some brute force methods,
like print statements to print messages out at certain points in the program or blink
some LEDs at strategic places, which means back to the editor, and the cycle
continues.
12.9.5 Using IDEs
Bringing up an ID E presents a workspace & w ith an IDE, a Project provides a
workspace where all the files for a program can be collected . We need to select the
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If set for a Windows Application in C, it brings up a template: A console C program
brings up a different template: Depending on the IDE, it may set up code blocks
automatically, indent as required, track variable names in colors, show comments. Compile? Just click the compile selection on the dropdown menu (or
press F9). Compiler results will show in one of the wind ows and in the log.
Compiler options and directories are set up using the options menus. As source files
are created, they are added to the project. The Rebuild selection rebuilds all the
files, first checking for the latest versions, then compiles and l inks to produce an
executable result. Errors on the compile or link? The offending code will be shown
in the code window. The statement containing the error or the lines around it is
known, since the compiler, linker, and editor are seamlessly connected. You can
run the executable from the IDE by selecting Run: The results show in a separate
window. Problems when running your new program? Usually IDEs provide an
option to create a debug version.
With a debug version, the IDE controls the execution of the program, allowing
insight to data variables and memory locations. Some IDEs show both the high
level source statements as well as the machine code. The debugger may include
options to "watch" local variables and track the contents of memory locations, offer line by line execution, provide the ability to set break points to run
to a certain point in the program, and the ability to step into or over function calls.
Some IDEs include emulators, allowing debugging in the IDE environment without
having to exp ort the code to the target device .

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12.9.6 Choosing AN IDE
When selecting an IDE you'll find there are a lot to choose from and the price can
vary from no cost to pricing options dependent on the environment and number of
users. The license type is important as well if you intend to produce commercial
code. Some things to check:
Does it provide support for you are?
ƒDevelopment platform? (Some only run on specific operating systems.)
ƒProgramming language(s)? (Some only support a specific language.)
ƒTarget environment(s)? (IDEs targeting desktops may not support android
environments.)
12.10 The Microcontroller Development Cycle

xAn Integrated Development Environment (IDE) is software that assists/supports programmers in developing software
xIDEs normally consist of a source code editor, a compiler, a linker/locater
and usually a debugger.
xSometimes, an IDE is devoted to one specific programming language or one
(family of) specific processor or hardware, But more often the IDEs support
multiple languages, processors, etc. Some commonly used IDEs for embedded systems are the GNU compiler collection (gcc), Eclipse, Delphi .
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xCross -compiler: A cross compiler is necessary to compile code for multiple
platforms from one development host. Direct c ompilation on the target
platform might be infeasible, for example on embedded systems with limited
computing resources.
xEditor: A source code editor is a text editor prog ram designed specifically
for editing source code to control embedded systems. It may be a standalone
application or it may be built into an integrated development environment
(e.g. IDE). Source code editors may have features specifically designed to
simpl ify and speed up input of source code, such as syntax highlighting and
auto complete functionality. These features ease the development of code
xCompiler: A compiler is a computer program that translates the source code
into computer language (object code). Commonly the output has a form
suitable for processing by other programs (e.g., a linker), but it may be a
human readable text file. A compiler translate s source code from a high level
language to a lower level language (e.g., assembly language or machine
language). The most common reason for wanting to translate source code is
to create a program that can be executed on a computer or on an embedded
system . The compiler is called a cross compiler if the source code is compiled
to run on a platform other than the one on which the cross compiler is run.
For embedded systems the compiler always runs on another platform, so a
cross compiler is needed.
xLinker: A linker or link editor is a program that takes one or more objects
generated by compilers and assembles them into a single executable program
or a library that can later be linked to in itself. All of the object files resulting
from compiling must be com bined in a special way before the program
locator will produce an output file that contains a binary image that can be
loaded into the target ROM. A commonly used linker/locater for embedded
systems isld (GNU).
12.11 Types of File Generated on cross comp ilation
The various 5 types of files generated during cross compilation process are as
follows –
1) List Files (.lst) – Listing file is generated during the cross -compilation
process. • It contains an information about the cross compilation process like
cross compiler details, formatted source text (‘C’ code), assembly code
generated from the source file, symbol tables, err ors and warnings detected
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2) Preprocessor Output file - It contains preprocessor output for preprocessor
instructions used in the source file. This file is used for verifying the operation
of Macros and preprocessor di rective
3) Object file (.obj file) - Cross -compiling each source module converts the
Embedded C/Assembly instructions and other directives present in the
module to an object (.obj file)
4) Map file (.map) - Also called as Linker List file. Map file contain s
information about the link/locate process and is composed of a number of
sections.
5) Hex File (.hex) - It is a binary executable file created from the source code.
The file created by linker/locater is converted into processor understandable
binary code. The tool used for converting and object file into a hex file is
known as object to Hex converter. Hex file have specific format and it varies
for different processor and controller. Two commonly used hex file format
are Intel Hex & Motorola Hex. Both Intel and Motorola hex file format
represent data in the form of ASCII codes.
12.12 Disassembler / De -Compiler :
A disassembler is a computer program that translates machine language into
assembly language the inverse operation to that of an assembler. Some disassemblers make use of the symbolic debugging information present in object
files such as ELF. A disassem bler differs from a decompiler, which targets a high -
level language rather than an assembly language . A decompiler is a computer
program translates an executable file in to a high -level source file that can be
recompiled successfully. A disassembler is software that converts machine language instructions into assembly language instructions
12.13 Simulators & Emulator
Some simulators go even a step further and include the whole system (simulation
of peripherals outside of the microcont roller). No matter how fast PC, there is no
simulator on the market that can actually simulate a microcontroller's behavior in
real-time. Simulating external events can become a time -consuming exercise, as
you have to manually create "stimulus" files that tell the simulator what external
waveforms to expect on which microcontroller pin. A simulator can also not talk
to your target system, so functions that rely on external components are difficult to
verify. For that reason simulators are best suited to tes t algorithms that run
completely within the microcontroller.
An emulator is a piece of hardware that ideally behaves exactly like the real
microcontroller chip with all its integrated functionality. It is the most powerful
debugging tool of all. A microcon troller's functions are emulated in real -time.
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An emulator is a hardware device or software program that enables one computer
system (also known as a host) to imitate the functions of another computer system
(known as the guest). It enables the h ost system to run software, tools, peripheral
devices and other components which are designed for the guest system. Emulators
can be of different types, replicating things such as hardware, software, OS or CPU.
Base Unit and Probe card: Many emulators cons ist of a base unit and a "probe
card". The base unit is connected to a PC via the serial, parallel or USB port. It
contains the majority of the emulator electronics, with the exception of the
emulation chip itself. The emulation chip is a special bond -out version of the actual
microcontroller and is mounted on a separate small PCB, called a probe card. This
probe card connects via a ribbon cable to the base unit and has a pin adapter at the
bottom, which allows the probe card to be plugged into a socket on the actual target
application board in place of the actual microcontroller.
12.14 Debugger:
A debugger is a computer program that is used to test and debug other programs.
A debugger is a piece of software running on the PC, which has to be tightly
integra ted with the emulator that you use to validate your code. A Debugger allows
you to download your code to the emulator's memory and then control all of the
functions of the emulator from a PC.
Debugging Tools:
When it comes to debugging your code and testin g your application there are
several different tools you can utilize that differ greatly in terms of development
time spend and debugging features available. In this section we take a look at
simulators and emulators.
12.15 Embedded Development Life-Cycle (EDLC)

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Concept:
xDescription of the original idea in a formal technical form (verbal requirements)
xInvestigation of the existing prototypes and/or models that match the idea
xComparative analysis of existing implementations
xProposal of implementation and materials options
Design: Functional Requirements:
xDevelopment of hardware functional specif ication
xDevelopment of software and firmware functional requirements
xAnalysis of the third -party requirements documentation
Architecture Design:
xDevelopment of the system architecture concept
xDesign of the mechanics parts of the system
xDevelo pment of hardware design documentation (including FPGA design)
xDevelopment of the detailed software design specification
xAnalysis of the third -party design documents
Hardware Modelling:
xSchematics design
xPCB Layout Design
xRe-engineering and repairing
xSamples & Prototypes Assembly
Prototyping:
xProduct prototyping (including all types of mechanics, hardware, software
and the whole system prototyping)
xMechanical parts manufacturing (including press forms manufacturing)
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xHardware development
xSoftware and firmware coding
xSystem integratio n (software with hardware and mechanics)
Implementation:
Porting:
xPorting of an existing system to a new hardware platform
xProduct certification (preparation of hardware and software for further
certification process)
System Optimization:
xOptimizati on of system performance, usability, cost, time to market and more
xAnalysis of the third -party implementation with suggested improvements
xSystem benchmarking documentation
Testing/Debugging:
xCreation of a sophisticated test system to verify a produ ct on each life cycle
stage
xDevelopment of testing documentation
xRemote hardware test system setup to allow customer run their own applications in a sophisticated hardware/software environment
xQuality improvement by analyzing the third -party products for existing
caveats and issues, and performing the corresponding debugging
Transition to Manufacturing:
xSchematics design
xPCB Layout Design
xRe-engineering and repairing
xSamples & Prototypes Assembly
Maintenance:
xDebu gging of the known problems
xDevelopment of an ECO system by developing additional demo applications
that can be used as a starting base for the system development
xSystem upgrades (new hardwa re, new software, new mechanics etc ).
12.16 TRENDS IN EMBEDDED INDUSTRY
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machine control applications to various other new verticals with the convergence
of communications. Various class es of embedded systems such as home media
systems, portable players, smart phones, embedded medical devices and sensors, automotive embedded systems have surrounded us and with continued convergence of communications and computing functions within these de vices,
embedded systems are transforming themselves into really complex systems, thus
creating newer opportunities and challenges to develop and market more powerful,
energy efficient processors, peripherals and other accessories
In embedded system is more than the electronics as most people perceive it. It has
electronics both digital and analog, special purpose sensors and actuators, software,
mechanical items etc., and with design challenges of space, weight, cost and power
consumption. In order to achieve key requirements, generally embedded systems
are restricted to limited resources in terms of computing, memory, display size etc.
With continued convergence of other technologies a lot more functionalities are
being pushed into embedded devices which were once part of traditional computing
platforms.
12.17 Summary
OS acts as Bridge between Application / Task & underlying system resources.
Primary function of OS is to make system convenient to use, Organise & manage
the system re sources efficiently. Also other functions of OS are Management of
Process, Memory, I/O, File system etc. So OS is called as Manager.
RTOS is an operating system intended to serve real time application that process
data as it comes in, mostly without buffer delay. It offers priority -based scheduling,
which allows you to separate analytical processing from non -critical processing.
Important components of RTOS system are: 1 ) The Scheduler, 2) Symmetric
Multiprocessing, 3) Function Library, 4) Memory Mana gement, 5) Fast dispatch
latency, and 6) User -defined data objects and classes .
Most of the commercial Embedded Operating systems available today are designed
for possible inclusion in Real time system. Process of selecting Operating system
for embedded system is outlined & reviewed. RTOS system occupy very less
memory and consume fewer resources Performance is the most important factor
required to be considered while selecting for a RTOS. General -Purpose Operating
System (GPOS) is used for desktop PC and l aptop while Real -Time Operating
System (RTOS) only applied to the embedded application. Real -time systems are
used in Airlines reservation sys tem, Air traffic control system etc. The biggest
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12.18 Questions
1. Explain the embedded Operating system with respect to
i) Tasks
ii) Task States
iii) Idle task
2. State & explain The Kernal in OS.
3. Explain the RTOS
4. Explain Scheduler useful in OS with respect to:
i) Scheduling Points
ii) Ready List
iii) Context Switch
5. Write a short note on Trends in Embedded industry.
6. Give the Real Time Characteristic of embedded operating system .
7. What is the process behind selection of RTOS.
8. Write note on Embedded system Development Environment – IDE.
9. Write note on Simulator & Emulator
10. Explain the phases of EDLC.
12.19 References & Future Reading
1) Book Programming in ANSI C by E Balgurusamy.
2) Book Embedded Systems Architecture, Programming & Design (Second
Edition / The McGraw Hill publications) by Raj kamal.
3) Introduction to Embedded system By Shibu K V (Tata McGraw Hill Publications)
4) Book Embedded System by Ashwini Somnathe & Abhijit Somnathe for
SYBSc IT (Sheth Publications)
5) www.google.com
6) www.youtube.com
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154Unit 5
13 EMBEDDED SYSTEMS: INTEGRATED
DEVELOPMENT ENVIRONMENT
Unit Structure
13.0 Objectives
13.1 Introduction
13.2 Embedded IDE
13.3 Types of file generated on cross compilation
13.4 Disassembler/ Decomipiler
13.5 Simulator
13.6 FirmWare Debugging
13.7 Review Questions
13.8 References & Further Reading
13.0 OBJECTIVES
After reading this chapter you will understand:
xEmbedded IDE
xTypes of files involved
xDisassembler/ Decompiler
xSimulator
xFirmware Debugging and Emulator
13.1 INTRODUCTION
This chapter explains the IDE used for embedded systems. It then explains the
different types of files that are generated on cross compilation. Then it gives an
account of utility tools like Disassembler/ Decompiler, Simulator and then
Firmwar e Debugging.
13.2 EMBEDDED IDE
xIntegrated Development Environment with respect to embedded system IDE
stands for an Integrated Environment for developing and debugging the target
processor specific embedded software.
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2. Cross Compiler(For Cross platform development and complier for the
same platform development)
3. Linker and debugger.
xSome IDEs may provide an interface to an emulator or device programmer.
xIDEs are used in embedded firmware development.
IDEs may be of two types:
1. Command Line Base
xTurbo C++ IDE is an example for a generic IDE with a Command Line
Interface.
2. GUI Base
yMicrosoft Visual Studio is an example of GUI base IDE.
yOthers examples are NetBeans, Eclipse.
13.3 TYPES OF FILE GENERATED ON CROSS
COMPILATION
Following are some of the files generated upon cross compilation:
1. List file.lst
2. Hex file.hex
3. Preprocessor output file
4. Map file .map
5. Obj file .obj
1 List File(.lst): -
• Listing file is generated during the cross -compilation process.
• It contains an information about the cross compilation process like
cross compiler details, formatted source text(‘C’ code), assembly code
generated from the source file, symbol tables, errors and warnings
detected during the cross -compilation process.
• The list file contain the following sections:
I. Page Header
• It indicates the compiler version name, source file name,
Date,
Page No.
• Example: C51 COMPILER V8.02 SAMPLE 05/23/2006
11:12:58 PAGE 1
II. Command Line
• It represents the entire command line that was used for
invoking the compiler.
• C51 COMPILER V8.02, COMPILATION OF MODULE
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• COMPILER INVOKED BY: C:\Keil\C51\BIN\C51.EXE
sample.c BROWSE DEBUG OBJECTTEXTEND CODE
LISTINCLUDE SYMBOLS
III. Source Code
• It contains source code along with line numbers
• Line level Source
1 //Sample.c for printing Hello World!
2 //Written by xyz
3 #include
1 //Body part starts 2
3
4
5
6 //Body part end
4 void main()
5 {
6 printf(“Hello World”);
7 }
8 //Header part ends
IV. Assembly listing
• It contains the assembly code generated by compiler for
even given ‘C’ code.
• ASSEMBLY LISTING OF GENERATED OBJECT
CODE;
• FUNCTION main(BEGIN)
;SOURCE LINE #5
;SOURCE LINE #6
0000 7BFF MOV R3,#0FFH
0002 7A00 R MOV R2,#HIGH?SC_0
V. Symbol listing
• It contains symbolic information about the various symbols
present in the cross compiled source file.
• Eg: NAME, TYPE, SFR, SIZE.

VI. Module Information
• The module information provides the size of initialized and
un-initialized memory areas defined by the source file.
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Module Information Static Overlayable
Code Size 9 -------------
Constant size 14 -------------
Bit size ------- -- -----------
END OF MODULE INFORMATION
VII. Warnings and Errors
• Warnings and Errors section of list file records the errors
encountered or any statement that may create issues in
application(Warnings), during cross compilation.
• ie:- C51 COMPILATION COMPLETE, 0WARNING(S),
0 ERROR(S).
3. Preprocessor Output File
• It contains preprocessor output for preproces sor instructions used in the
source file.
• This file is used for verifying the operation of Macros and preprocessor
directive.
5. Object File(.OBJ File)
• Cross -compiling each source module converts the Embedded C/Assembly instructions and other directives present in the module to
an object(.OBJ file)
4. Map File(.MAP)
• Also called as Linker List file. Map file contains information about the
link/locate process and is composed of a number of sections described
below:
I. Page Header
Each MAP file contains a header which indicates the linker
version number, date, time and page number.
II. Command Line
Represents the entire command line that was used for invoking
the linker.
III. CPU Details
It contains details about the target CPU and its memor y model
which includes information on internal data memory, external
data memory, paged data memory, etc.
IV. Input Modules
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V. Memory Map
It lists the starting address, length, relocation type and name of
each segment in the program
VI. Symbol Table
It contains the name, value and type for all symbols from
different input modules.
VII. Inter Module Cross Reference
It includes the section name, memory type and module names in
which it is defined and all modules where it is accessed.
Ex. NAME…………………….USAGE……… .……………..
MODULE NAMES
?CCCASE…………………CODE; ……………………… ?
C?CCASE PRINTF
?C?CLDOPTR……………CODE; ?................................. C?
CLDOPTR PRINTF
?C?CSTPTR………………CODE; ……………………. ?C
?CSTPTR PRINTF
VIII. Program Size
It contains the size of various memory areas,
constants and code space for the entire application Ex. Program
Size: data=80.1 xdata=0 code 2000
IX. Warnings and Errors
It contains the warnings and errors that are generated while
linking a program. It is used in debugging link errors
2. HEX FILE (.hex file)
i. It is a binary executable file created from the source code.
ii. The file created by linker/locater is converted into processor understandable binary code.
iii. The tool used for converting and object file into a hex file is known as
object to Hex converter.
iv. Hex file have specific format and it varies for different processor and
controller. Two commonly used hex file format are:
A. Intel Hex
B. Motorola Hex.
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13.4 DISASSEMBLER/ DECOMPILER
xA Disassembler/ Decompiler is a reverse engineering tool.
xReverse Engineering is used in embedded system to find out the secret behind
the working of a proprietary product.
xA DISASSEMBLER is a utility program which converts machine codes into
target processor specific assembly code/instruction.
xThe process of converting machine codes to assembly code is called
disassembling.
xA DECOMIPILER is a utility program for translating machine codes into
corresponding high level language instruction.
xA decompiler performs the reverse operation of a compiler/cross -compiler.
13.5 SIMULATOR
xSimulators are used for embedded firmware debugging.
xSimulator simulates the target hardware, while the code execution can be
inspected.
xSimulators have the following characteristics which make them very much
favorable:
9 Purely software based
9 No need of target system (hardware)
9 Support only for basic operations
9 Cannot Support or lack real time behavior
xAdvantages
1. Simple and straight forward.
x Simulators are a software utility with assumptions about the underlying
hardware. So it only requires concentrating on debugging of the code,
hence straight forward.
2. No Hardware
x Simulators are purely software oriented.
x The IDE simulates t he target CPU. The user needs to know only about
the target specific details like memory map of various devices.
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3. Simulation options
x Simulators provide various simulation options like I/O peripherals or
CRO or Logic analyzers.
x Simulators I/O support can be used to edit values for I/O registers.
4. Simulation of abnormal conditions
x Using simulator the code can be tested for any desired value.
x This helps to study the code behavior in abnormal conditions without
actually testing it on the hardware.
xx Disadvantages
I Lack of real time behavior
xx A simulator assumes the ideal condition for code execution.
xx Hence the developer may not be able to debug the code
under all possible combinations of input.
xx The results obtained in simulation may deviate from actual
results on target hardware.
II Lack of real timeliness
xx The I/O condition in hardware is unpredictable. So the
output of simulation is usually under ideal condition and
hence lacks timeliness.
13.6 FIRMWARE DEBUGGING
xx Debugging in embedded application is the process of diagnosing the firmware execution, monitoring the target processor’s registers and memory
while the firmware is running and checking the signals on various buses of
hardware.
xx Debugging is classified into Hardware Debugging and Firmware Debugging.
xx Hardware Debugging deals with debugging the various as pects of hardware
involved in the embedded system.
xx The various tools used for hard ware debugging are Multimeter, CRO, Logic
Analyzers and Function Generators.
xx Firmware Debugging involves inspecting the code, its execution flow,
changes to different registers on code execution.
xx It is done to find out the bugs or errors in code which produces unexpected
behavior in the system.
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xx Some to the tools used are Simulators and Emulators.
xx Emulators
xx The terms simulators and emulators are very confusing but their basic
functionality is the same i.e. to debug the code. There is a difference in
which this is achieved by both the tools.
xx A simulator is a utility program that duplicates the target CPU and simulates the features and instructions supported by target CPU whereas an Emulator is a self contained hardware device which
emulates the target CPU.
xx The Emulator hardware contains the necessary emulation logic and is
connected to the debugging application that runs on the host PC.
xx The Simulator µVLPXODWHV¶ while the Emulator µHPXODWHV¶
13.7 SUMMARRY
x Integrated Development Environment with respect to embedded
system IDE stands for an Integrated Environment for developing and
debugging the target processor specific embedded software.
x A DISASSEMBLER is a utility program which converts machine
codes into target processor specific assembly code/instruction .
x Simulator simulates the target hardware, while the code execution can
be inspected.
13.8 REVIEW QUESTIONS
1. Write a Short note on Embedded IDE
2. What is Cross - Compilation? List the files that are generated upon cross
compilation
3. Explain the contents of .MAP file.
4. Explain the contents of .LST file.
5. Write short notes on :
I. .OBJ File
II. .HEX File
III. Preprocessor Output File
13.8 REFERENCES & FURTHER READING
Introduction to Embedded systems – Shibu K. V
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162Unit 5
14 EMBEDDED DEVELOPMENT
LIFE CYCLE
Unit Structure
14.0 Objectives
14.1 Introduction
14.2 EDLC
14.2.1 Need For ELDC
14.2.2 Objectives
14.3 Different Phases of EDLC
14.4 ELDC Approaches
14.5 Review Questions
14.6 References & Further Reading
14.0 OBJECTIVES
After Reading this chapter you will understand
xThe Embedded Development Life Cycle
xPhases Involved in the EDLC
14.1 INTRODUCTION
Just like the SDLC used in Software Development, there is EDLC used in
Embedded product development. This chapter explains what is the EDLC, its
objectives, the phases that are involved in the EDLC.
14.2 EMBEDDED PRODUCT DEVELOPMENT LIFE CYCLE
(EDLC)
xEDLC is Embedded Product Development Life Cycle
xIt is an Analysis – Design – Implementati on based problem solving approach
for embedded systems development.
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xAnalysis involves understanding what product needs to be developed
xDesign involves what approach to be used to build the product
xImplementation is developing the product by realizing the design.
14.2.1 Need for EDLC
x EDLC is essential for understanding the scope and complexity of the work
involved in embedded systems development
x It can be used in any developing any embedded product
x EDLC defines the interaction and activities among various groups of a
product development phase.
Example: -project management, system design
14.2.2 Objectives of EDLC
x The ultimate aim of any embedded product in a commercial production setu p
is to produce Marginal benefit
x Marginal is usually expressed in terms of Return On Investment
x The investment for product development includes initial investment, manpower, infrastructure investment etc.
x EDLC has three primary objectives are:
i. Ensure that high quality products are delivered to user
x Quality in any product development is Return On Investment achieved by
the product
x The expenses incurred for developing the product the product are:
ͻInitial investment
ͻDeveloper recruiting
ͻTraining
ͻInfrastructure requirement related
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ii. Risk minimization defect prevention in product development through project management
x In which required for product development ‘loose’ or ‘tight’ project
management
x ‘project management is essential for ’ predictability co -ordination and risk
minimization
x Resource allocation is critical and it is having a direct impact on investment
x Example: - Microsoft @ Project Tool
iii. Maximize the productivity
x Productivity is a measure of efficiency as well as Return On Investment
x This productivity measurement is based on total manpower efficiency
x Productivity in which when product is increased then investment is fall down
x Saving manpower
14.3 DIFFERENT PHASES OF EDLC
The following figure depicts the different phases in EDLC:
Figure : Phases of EDLC
ϭϭ͘͘Need
ͻThe need may come from an individual or from the public or from a
company.
ͻ‘Need’ should be articulated to initiate the Development Life Cycle; a
‘Concept Proposal’ is prepared which is reviewed by the senior
management for approval.
ͻNeed can be visualized in any one of the following three needs:
ϭ͘New or Custom Product Development.
Ϯ͘Product Re-engineering.
ϯ͘Product Maintenance.
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2. Conceptualization
ͻDefines the scope of concept, performs cost benefit analysis and
feasibility study and prepare project management and risk management
plans.
ͻThe following activities performed during this phase:
ϭ͘Feasibility Study : Examine the need and suggest possible
solutions.
Ϯ͘Cost Benefit Analysis (CBA): Revealing and assessing the total
development cost and profit expected from the product.
ϯ͘Product Scope: Deals with the activities involved in the product
to be made.
ϰ͘Planning Activities: Requires various plans to be developed first
before development like Resource Planning & Risk management
Plans.
3. Analysis
ͻThe product is defined in detail with respect to the inputs, processes,
outputs, and interfaces at a functional level.
ͻThe various activities performed during this phase..
ͻAnalysis and Documentations: This activity consolidates the business
needs of the product under development.
ͻRequirements that need to be addressed..
‰Functional Capabilities like performance
‰Operational and non -operational quality attribute
‰Product external interface requirements
‰Data requirements
‰User manuals
‰Operational requirements
‰Maintenance requirements
‰General assumptions
xDefining Test Plan and Procedures : The various type of testing
performed in a product development are:
‰Unit testing – Testing Individual modules
‰Integration testing – Testing a group of modules for required
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‰User acceptance testing - Testing the product to meet the end
user requirements.
4.Design
ͻThe design phase identifies application environment and creates an
overall architecture for the product.
ͻIt starts with the Preliminary Design. It establishes the top level
architecture for the product. On completion it resembles a ‘black box’
that defines only the inputs and outputs. The final product is called
Prelimi nary Design Document (PDD).
ͻOnce the PDD is accepted by the End User the next task is to create the
‘Detailed Design’.
ͻIt encompasses the Operations manual design, Maintenance Manual
Design and Product Training material Design and is together called the
‘Detailed Design Document’.
5. Development and Testing
ͻDevelopment phase transforms the design into a realizable product.
ͻThe detailed specification generated during the design phase is translated into hardware and firmware.
ͻThe Testing phase can be divided into independent testing of firmware
and hardware that is:
‰Unit testing
‰Integration testing
‰System testing
‰User acceptance testing
6. Deployment
ͻDeployment is the process of launching the first fully functional model
of the product in the market.
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ͻIt is also known as First Customer Shipping (FCS).
ͻTasks performed during this phase are:
ͻNotification of Product Deployment: Tasks performed here include:
‰Deployment schedule
‰Brief description about the product
‰Targeted end user
‰Extra features supported
‰Product support information
ͻExecution of training plan
Proper training should be given to the end user top get them acquainted
with the new product.
ͻProduct installation
Install the product as per the installation document to ensure that it is
fully functional.
xProduct post Implementation Review
After the product launch, a post implementation review is done to test
the success of the product.
ϳϳ͘͘Support
ͻThe support phase deals with the operational and maintenance of the
product in the production environment.
ͻBugs in the product may be observed and reported.
ͻThe support phase ensures that the product meets the user needs and it
continues functioning in the production environment.
ͻActivities involved under support are
‰Setting up of a dedicated support wing : Involves providing 24
x 7 supports for the product after it is launched.
‰Identify Bugs and Areas of Improvement: Identify bugs and
take measures to eliminate them.
8. Upgrades
ͻDeals with the development of upgrades (new versions) for the product
which is already present in the market.
ͻProduct upgrade results as an output of major bug fixes.
ͻDuring the upgrade phase the system is subject to design modification
to fix the major bugs reported.
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9. Retirement/Disposal
ͻThe retirement/disposal of the product is a gradual process.
ͻThis phase is the final phase in a product development life cycle where
the product is declared as discontinued from the market.
ͻThe disposal of a product is essential due to the following reasons
‰Rapid technology advancement
‰Increased user needs
14.4 ELDC APPROACHES
Following are some of the different types of approaches that can be used to model
embedded products.
1. Waterfall or Linear Model
2. Iterative/ Incremental or Fountain Model
3. Prototyping Model
4. Spiral Model
14.6 SUMMARRY
x Objectives of EDLC: i. Ensure that high quality products are delivered to user
ii. Risk minimization defect prevention in product development through project management iii. Maximize the productivity
x Different phases of EDLC
14.5 REVIEW QUESTIONS
1. What is EDLC? Why is it needed? What are its objectives?
2. Draw an neat labeled diagram of the phases of the EDLC and explain any
two phases in detail.
14.6 REFERENCES & FURTHER READING
Introduction to Embedded systems – Shibu K. V

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Unit 5
15 TRENDS IN EMBEDDED SYSTEMS
Unit Structure
15.0 Objectives
15.1 Introduction
15.2 Processor Trends
15.3 Operating System Trends
15.4 Development Language Trends
15.5 Open Standards, Frameworks and alliances
15.6 Bottlenecks faced by Embedded Industry
15.7 Review Questions
15.8 References & Further Reading
15.0 OBJECTIVES
After reading this chapter you will understand:
x Different trends in the embedded industry related to:
x Processor Trends
x Operating System Trends
x Development Language Trends
x Open Standards, Frameworks and alliances
x Bottlenecks faced by Embedded Industry
15.1 INTRODUCTION
This concluding chapter describes the trends in the embedded systems industry.
15.2 PROCESSOR TRENDS
x There have been tremendous advancements in the area of processor design.
x Following are some of the points of difference between the first generation
of processor/controller and today’s processor/ controller.
o Number of ICs per chip : Early processors had a few number of IC/gates per chip. Today’s processors with Very Large Scale munotes.in

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Integration (VLSI) technology can pack together ten of thousands of
IC/gates per processor.
o Need for individual components: Early processors need different
components like brown out circuit, timers, DAC /ADC separately
interfaced if required to be used in the circuit. Today’s processors have
all these components on the same chip as the processor.
o Speed of Execution: Early proc essors were slow in terms of number
of instructions executed per second. Today’s processor with advanced
architecture support features like instruction pipeline improving the
execution speed.
o Clock frequency: Early processors could execute at a frequency of a
few MHz only. Today’s processors are capable of achieving execution
frequency in rage of GHz.
o Application specific processor: Early systems were designed using
the processors available at that time. Today it is possible to custom
create a processor according to a product requirement.
x Following are the major trends in processor architecture in embedded
development.
A. System on Chip (SoC)
x This concept makes it possible to integrate almost all functional
systems required to build an embedded product into a single chip.
x SoC are now available for a wide variety of diverse applications
like Set Top boxes, Media Players, PDA, etc.
x SoC integrate multiple functional components on the same chip
thereby saving board space which helps to miniaturize the overall
design.
B. Multicore Processors/ Chiplevel Multi Processor
x This concept employs multiple cores on the same processor chip
operating at the same clock frequency and battery.
x Based on the number of cores, these processors are know n as:
o Dual Core – 2 cores
o Tri Core – 3 cores
o Quad Core – 4 cores
x These processors implement multiprocessing concept where each
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C. Reconfigurable Processors
x It is a processor with reconfigurable hardware features.
x Depending on the requirement, reconfigurable processors can change their functionality to adapt to the new requirement. Example: A reconfigurable processor chip can be configured as
the heart of a camera or that of a med ia player.
x These processors contain an Array of Programming Elements
(PE) along with a microprocessor. The PE can be used as a
computational engine like ALU or a memory element.
15.3 OPERATING SYSTEM TRENDS
x The advancements in processor technology have caused a major change in
the Embedded Operating System Industry.
x There are lots of options for embedded operating system to select from which
can be both commercial and proprietary or Open Source.
x Virtualization concept is brought in picture in the embedded OS industry
which replaces the monolithic architecture with the microkernel architecture.
x This enables only essential services to be contained in the kernel and the rest
are installed as services in the user space as is done in Mobile phones.
x Off the shelf OS customized for specific device requirements are now
becoming a major trend.
15.4 DEVELOPMENT LANGUAGE TRENDS
There are two aspects to Development Languages with respect to Embedded
Systems Development
A. Embedded Firmware
x It is the application that is responsible for execution of embedded
system.
x It is the software that performs low level hardware interaction, memory
management etc on the embedded system.
B. Embedded Software
x It is the software that runs on the host computer and is responsible for
interfacing with the embedded system.
x It is the user application that executes on top of the embedded system
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Early languages available for embedded systems development were limited to C &
C++ only. Now languages like Microsoft C$, ASP.NET, VB, Java, etc are
available.
A. Java
x Java is not a popular language for embedded systems development due
to its nature of execution.
x Java programs are compiled by a compiler into bytecode. This bytecode
is then converted by the JVM into processor specific object code.
x During runtime, this interpretation of the bytecode by the JVM makes
java applications slower that other c ross compiled applications.
x This disadvantage is overcome by providing in built hardware support
for java bytecode execution.
Figure: Java based Embedded Application Development
x Another technique used to speed up execution of java bytecode is using
Just In Time (JIT) compiler. It speeds up the program execution by
caching all previously executed instruction.
x Following are some of the disadvantage of Java in Embedded Systems
deve lopment:
o For real time applications java is slow
o Garbage collector of Java is non -deterministic in behavior which
makes it not suitable for hard real time systems.
o Processors need to have a built in version of JVM
o Those processors that don’t have JVM require it to be ported for
the specific processor architecture.
o Java is limited in terms of low level hardware handling compared
to C and C++
o Runtime memory requirement of JAVA is high which is not
affordable by embedded systems.
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B. .NET CF
x It stands for .NET Compact Framework.
x .NET CF is a replacement of the original .NET framework to be used
on embedded systems.
x The CF version is customized to contain all the necessary components
for application development.
x The Original version of . NET Framework is very large and hence not a
good choice for embedded development.
x The .NET Framework is a collection of precompiled libraries.
x Common Language Runtime (CLR) is the runtime environment of
.NET. It provides functions like memory managemen t, exception
handling, etc.
x Applications written in .NET are compiled to a platform neutral language called Common Intermediate Language (CIL).
x For execution, the CIL is converted to target specific machine instructions by CLR.

Figure: .NET based Embedded Application Development
15.5 OPEN STANDARDS, FRAMEWORKS AND ALLIANCES
Standards are necessary for ensuring interoperability. With diverse market it is
essential to have formal specifications to ensure interoperability.
Following are some of the popular strategic alliances, open source standards and
frameworks specific to the mobile handset industry.
A. Open Mobile Alliance (OMA)
x It is a standard body for creating open standards for mobile industry.
x OMA is the Leading Industry Forum for Developing Market Driven –
Interoperable Mobile Service Enablers
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x OMA was formed in June 2002 by the world’s leading mobile operators, device and network suppliers, information technology companies and content and service providers.
x OMA delivers open sp ecifications for creating interoperable services
that work across all geographical boundaries, on any bearer network.
OMA’s specifications support the billions of new and existing fixed
and mobile terminals across a variety of mobile networks, including traditional cellular operator networks and emerging networks supporting machine -to-machine device communication.
x OMA is the focal point for the development of mobile service enabler
specifications, which support the creation of interoperable end -to-end
mobile services.
xGoals of OMA
x Deliver high quality, open technical specifications based upon market
requirements that drive modularity, extensibility, and consistency
amongst enablers to reduce industry implementation efforts.
x Ensure OMA service enabler specifications provide interoperability
across different devices, geographies, service providers, operators, and
networks; facilitate interoperability of the resulting product
implementations.
x Be the catalyst for the consolidation of standards activity within the mobile data service industry; working in conjunction with other existing standards organizations and industry fora to improve interoperability and decrease operational costs for all involved.
x Provide value a nd benefits to members in OMA from all parts of the
value chain including content and service providers, information
technology providers, mobile operators and wireless vendors such that
they elect to actively participate in the organization.
(Source : http://www.openmobilealliance.org )
B. Open Handset Alliance (OHA)
x The Open Handset Alliance is a group of 84 technology and mobile
companies who have come together to accelerate innovation in mobile and offer consumers a richer, less expensive, and better mobile experience. Together they have developed Android™, the first complete, open, and free mobile platform and are committed to
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x Members of OHA include mobile operators, handset manufacturers,
semiconductor companies, software companies, and commercialization
companies.
(Source : http://www.openhandsetalliance.com/ )
C. Android
x Android is an operating system based on the Linux kernel, and designed
primarily for touchscreen mobile devices such as smartphones and
tablet computers.
x Initially developed by Android, Inc., which Google supported financially and later bought in 2005, Android was unveiled in 2007
along with the founding of the Open Handset Alliance: a consortium of
hardware, software, and telecommunication companies devoted to
advancing open standards for mobile devices.
x The first publicly -available Sm artphone to run Android, the HTC
Dream, was released on October 18, 2008
Source: http://en.wikipedia.org/wiki/Android_(28operating_system)
D. Openmoko
x Openmoko is a project to create a family of open source mobile phones,
including the hardware specification and the operating system.
x The first sub -project is Openmoko Linux, a Linux -based operating
system designed for mobile phones, built using free software.
x The second sub -project is developing hardware devices on which
Openmoko Linux runs.
(Source: http://en.wikipedia.org/wiki/Openmoko )
15.6 Bottlenecks faced by Embedded Industry
Following are some of the problems faced by the embedded devices
industry:
A. Memory Performance
x The rate at which processors can process may have increased considerably but rate at which memory speed is increasing is slower.
B. Lack of Standards/ Conformance to standards
x Standards in the embedded industry are followed only in certain
handful areas like Mobile handsets.
x There is growing trend of proprietary architecture and design in other
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C. Lack of Skilled Resource
x Most important aspect in the development of embedded system is
availability of skilled labor. There may be thousands of developers who
know how to code in C, C++, Java or .NET but very few in embedded
software.
15.7 REVIEW QUESTIONS
1. Write a short note on Processor Trends in Embedded Systems
2. Explain the Embedded Operating System Trends
3. Write Short notes on Embedded Development Language Trends
4. Explain Open Standards, Frameworks and alliances
5. Write short note on Bottlenecks faced by Embedded Industry
15.8 REFERENCES & FURTHER READING
Introduction to Embedded systems – Shibu K. V

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